Which of the following describes an experiment?

Correct Answer: D

Rationale: Option D describes an experiment because it involves testing the effects of a new drug on a group of participants. In an experiment, researchers intentionally manipulate an independent variable (in this case, the new drug) to observe its effects on a dependent variable (the participants' health outcomes). This method allows for establishing cause-and-effect relationships between variables, which is a key characteristic of experimental research design. Choices A, B, and C do not represent experiments. Choice A involves observational analysis of math grades, choice B involves observational analysis of health trends, and choice C involves a survey, none of which involve manipulating variables to establish cause-and-effect relationships.

Correct Answer: C

Rationale: The correct answer is C: 'Specialized structures within a cell.' An organelle is a specialized subunit within a cell that has a specific function. Organelles are membrane-bound structures found within the cytoplasm of eukaryotic cells, each performing distinct roles that contribute to the overall functioning of the cell. Choices A, B, and D are incorrect. Option A describes the glycocalyx, which is a layer of polysaccharides outside the plasma membrane of cells. Option B refers to prions, abnormal infectious proteins. Option D defines an organ, a collection of tissues used to serve a specific function, rather than an organelle within a cell.

Correct Answer: D

Rationale: The correct answer is D. The primary functions of a healthy immune system do not involve creating infections. A healthy immune system helps the body avoid infections by providing defense mechanisms, detects infections by recognizing harmful pathogens, and eliminates infections by attacking and clearing out pathogens. Creating infections goes against the protective role of the immune system and is not a function it performs. Therefore, choices A, B, and C are correct functions of a healthy immune system, while choice D is incorrect.

Correct Answer: A

Rationale: The correct answer is A: 'to test a hypothesis.' The primary purpose of conducting an experiment is to test a hypothesis. This process allows researchers to gather empirical evidence to either support or refute a proposed hypothesis. By systematically manipulating variables and observing outcomes, scientists can draw conclusions about the relationships between these variables. Choice B, 'to collect data,' is a common step within an experiment, but the ultimate goal is to test a specific hypothesis. Choice C, 'to identify a control state,' is not the primary purpose but rather a methodological consideration within an experiment to ensure reliable results. Choice D, 'to choose variables,' is a step that is typically done before conducting the experiment and is not the primary purpose of the experiment itself.

Correct Answer: B

Rationale: The possible conclusion that can be drawn from every child in a certain family suffering from autism is that autism may be genetic. The fact that every child in the family has autism suggests a strong genetic influence on the condition within this particular family. This does not necessarily mean that autism is solely genetic in all cases, but in this specific family, the pattern of all children being affected points towards a genetic connection. Choice A is incorrect as the information provided does not suggest that autism is lethal. Choice C is incorrect as there is no evidence to support a relationship between autism and traditional nuclear family structures. Choice D is incorrect because a conclusion can be drawn from the given evidence, indicating a potential genetic link within this specific family.

Correct Answer: D

Rationale: Enzymes are protein molecules that serve as catalysts for certain biological reactions. Enzymes are biological molecules that speed up chemical reactions in living organisms by lowering the activation energy required for the reactions to occur. They are typically proteins that have specific shapes and active sites that allow them to interact with specific substrates and facilitate reactions without being consumed themselves. The other choices are incorrect because enzymes are not irrelevant, acidic, or lipid molecules; they are primarily proteins known for their catalytic properties.

Correct Answer: A

Rationale: The correct answer is A: Kidneys. The kidneys are not part of the circulatory system. While the circulatory system includes the heart, blood, and blood vessels (arteries, veins, capillaries), the kidneys belong to the urinary system. The kidneys are responsible for filtering waste products from the blood and producing urine. Choice B, the heart, is a vital organ in the circulatory system responsible for pumping blood. Choice C, blood, is a key component of the circulatory system that carries oxygen and nutrients to the body's tissues. Choice D, blood vessels (arteries, veins, capillaries), facilitate the circulation of blood throughout the body, playing a crucial role in the circulatory system.

Correct Answer: B

Rationale: The correct answer is B: Walking. Walking is not directly controlled by the autonomic nervous system. Walking is a voluntary action governed by the somatic nervous system, which controls voluntary skeletal muscle movement. The autonomic nervous system, on the other hand, regulates functions that are involuntary, such as digestion, heartbeat, and temperature regulation. Choices A, C, and D are all functions controlled by the autonomic nervous system. Digestion involves processes like peristalsis and secretion of digestive enzymes, heartbeat is regulated by the autonomic nervous system to maintain blood pressure and circulation, and temperature regulation includes responses like sweating or shivering to maintain body temperature within a narrow range.

Correct Answer: C

Rationale: Laryngeal damage would most affect the function of singing. The larynx, or voice box, houses the vocal cords responsible for producing sound during singing. Damage to the larynx can impair the ability to phonate and control pitch, tone, and quality of the voice, which are crucial for singing. Choices A, B, and D are unrelated to the larynx. Blinking is controlled by the facial nerve, walking involves motor functions and coordination, and hearing is related to the ear structures and auditory nerves.