Correct Answer: B

Rationale: A myocardial infarction, commonly known as a heart attack, occurs when a blockage forms in a coronary artery, leading to reduced blood flow to the heart muscle. Atherosclerosis refers to the buildup of plaque in the arteries, which can lead to blockages but is not the name for this specific condition. Angina pectoris is chest pain or discomfort due to inadequate blood supply to the heart muscle, which is a precursor to a heart attack but not the name for this condition. A heart murmur is an abnormal sound heard during a heartbeat, often due to turbulent blood flow, and is not related to a blockage in a coronary artery.

Correct Answer: C

Rationale: A) Convergent evolution refers to the process by which unrelated species evolve similar traits due to similar environmental pressures. This does not involve reciprocal influence between species. B) Divergent evolution refers to the process by which two or more related species become more dissimilar over time due to different selection pressures. This also does not involve reciprocal influence between species. C) Coevolution is the process by which two or more species reciprocally influence each other's evolution through selection pressures exerted on one another. This can lead to a close ecological relationship between the species, such as in predator-prey interactions or mutualistic relationships. D) This option is a duplicate of option C.

Correct Answer: A

Rationale: When a wave passes from one medium to another with the same speed, its frequency remains unchanged. Frequency is a characteristic of the source of the wave and does not depend on the medium through which the wave is traveling. Wavelength and speed of the wave can change when passing from one medium to another, but frequency remains constant. This is because the frequency of a wave is determined by the source that produces it, and as long as the speed remains constant, the frequency will not be altered. Amplitude, on the other hand, can change based on factors like energy loss or gain, but it is not a property that remains constant when a wave moves between different mediums with the same speed. Speed, although important for the wave's propagation, is not the property that remains unchanged when the wave transitions between mediums with the same speed. Therefore, the correct answer is frequency.

Correct Answer: B

Rationale: A) Incorrect. Gene therapy does aim to modify existing genes within body cells, but genetic engineering does not necessarily manipulate genes in embryos to be passed on to offspring. Genetic engineering can involve modifying genes in any type of cell, not just embryos. B) Correct. Gene therapy is a medical intervention that aims to treat genetic diseases by correcting or replacing faulty genes within an individual's body cells. On the other hand, genetic engineering involves modifying genes to enhance specific traits or eliminate undesirable ones, often in the context of agriculture or biotechnology. C) Incorrect. While both gene therapy and genetic engineering involve altering DNA sequences, the distinction lies in the target cells. Gene therapy targets somatic cells (non-reproductive cells), while genetic engineering typically involves modifying germline cells (reproductive cells that can pass on genetic changes to offspring). D) Incorrect. There is

Correct Answer: B

Rationale: The correct answer is B, Chlorine. Chlorine is the element present in household bleach that provides disinfectant properties due to its oxidizing ability. Chlorine is effective in killing bacteria and other microorganisms. Sodium (Choice A) is a component of common table salt and not the active disinfectant in bleach. Fluorine (Choice C) is not typically found in household bleach but is used in fluoride products. Iodine (Choice D) is used as a disinfectant in some contexts but is not the primary element in household bleach.