During which of the following stages does crossing over occur?

Correct Answer: B

Rationale: Crossing over occurs during Prophase I of meiosis. This stage is specifically associated with genetic recombination, where homologous chromosomes exchange genetic material. This process contributes to genetic diversity by creating new combinations of alleles. Choices A, C, and D are incorrect. In mitosis, crossing over does not occur as it involves the separation of replicated chromosomes. Meiosis Prophase II is focused on the reformation of nuclei and does not involve crossing over. Interphase is a stage where the cell prepares for division and is not associated with crossing over.

Correct Answer: B

Rationale: The correct answer is B, Somatic. The somatic nervous system controls voluntary movements of skeletal muscles. It is responsible for carrying sensory and motor information to and from the central nervous system. Choices A, C, and D are incorrect. The autonomic nervous system (choice A) controls involuntary functions such as heart rate and digestion. The sympathetic (choice C) and parasympathetic (choice D) nervous systems are subdivisions of the autonomic nervous system and are responsible for the body's fight-or-flight response and rest-and-digest functions, respectively.

Correct Answer: B

Rationale: In the scientific method, defining the problem is typically the initial step. Before gathering qualitative data, it is essential to clearly outline and understand the issue or question being addressed. This step helps in guiding the research process and ensures that the data collected are relevant to the problem at hand. Communicating with a scientific journal (Choice A) is not a standard step in the scientific method; it comes after the research is conducted. Developing a hypothesis (Choice C) usually follows defining the problem and precedes data collection. Categorizing data for statistical analysis (Choice D) occurs after data collection, not before gathering qualitative data.

Correct Answer: C

Rationale: Natural Killer cells are a crucial component of the innate immune response. They play a significant role in defending against infected or cancerous cells through their ability to identify and kill abnormal cells. B-cells (Choice A) and Cytotoxic T-cells (Choice B) are part of the adaptive immune response, which involves a more specific and targeted response to pathogens. Antigen-Presenting Cells (Choice D) are also part of the adaptive immune response, where they present antigens to activate other immune cells.

Correct Answer: D

Rationale: The correct answer is D: 'Takes shape of container.' Liquids exhibit the property of taking the shape of their container while maintaining a fixed volume. This is due to the ability of liquid particles to flow and move freely within the container. Choices A, B, and C are incorrect. Choice A, 'High atomic attraction,' is not a general property of liquids as the level of attraction between liquid particles can vary. Choice B, 'Fixed volume,' is partially correct as liquids do have a fixed volume, but they do not have a fixed shape. Choice C, 'Low pressure,' is not a defining property of liquids.