The following drugs can depress the sympathetic activity EXCEPT:

Correct Answer: C

Rationale: The correct answer is C: Phenylephrine. Phenylephrine is a sympathomimetic drug that stimulates the sympathetic nervous system, leading to vasoconstriction and increased heart rate. In contrast, choices A, B, and D all work to depress sympathetic activity by different mechanisms. Clonidine is an alpha-2 adrenergic agonist that decreases sympathetic outflow. Reserpine inhibits the storage of norepinephrine, leading to decreased sympathetic activity. Labetalol is a non-selective beta blocker that blocks beta-adrenergic receptors, reducing sympathetic effects. Therefore, Phenylephrine is the only drug among the options that does not depress sympathetic activity.

Correct Answer: A

Rationale: The correct answer is A: "Don't stop taking this medication without a doctor's advice first." Abruptly stopping a β-blocker can lead to severe adverse reactions like rebound hypertension, angina exacerbation, or arrhythmias due to sudden withdrawal. This instruction is crucial to prevent these potentially dangerous consequences. Explanation for why other choices are incorrect: B: β-blockers are not known to commonly cause urinary frequency, so this warning is unnecessary. C: Blurred vision is not a common side effect of β-blockers, so this warning is irrelevant. D: While constipation can be a side effect of some medications, it is not a prominent side effect of β-blockers, so this advice is not essential for patients taking β-blockers.

Correct Answer: D

Rationale: The correct answer is D because removing hawks would lead to an increase in both grasshoppers and rabbits. Hawks are natural predators of both grasshoppers and rabbits. With fewer hawks preying on them, the populations of grasshoppers and rabbits would increase due to reduced predation pressure. Choice A is incorrect because the removal of hawks would lead to an increase in grasshoppers and rabbits, not no change. Choice B is incorrect because removing hawks would not cause a decrease in grasshoppers but rather an increase. Choice C is incorrect because the removal of hawks would actually result in an increase in the populations of both grasshoppers and rabbits, not no change.

Correct Answer: C

Rationale: The correct answer is C: filtrate, evaporation. In process 1, aqueous sodium chloride would form the filtrate after filtration, as the solid residue is left behind. In process 2, evaporation is used to separate the solvent (water) from the dissolved salt, leaving behind the pure salt. Choice A is incorrect because residue is the solid left behind, not the liquid portion (filtrate). Choice B is incorrect as filtration results in the filtrate, not the residue. Choice D is incorrect as the filtrate undergoes evaporation, not filtration.

Correct Answer: A

Rationale: The correct answer is A: the distance travelled by light in a vacuum in 1 year. Light-year is a unit of astronomical distance, not time. Light travels at a constant speed in a vacuum, approximately 299,792 kilometers per second. In one year, light can travel about 9.46 trillion kilometers, which is defined as one light-year. Choices B, C, and D are incorrect because they do not accurately define a light-year in terms of distance traveled by light in a vacuum over a specific time period.