Radioiodines in the body emit:

Correct Answer: A

Rationale: The correct answer is A: Radioiodines in the body emit mainly β radiations. This is because radioiodines typically decay by β- decay, releasing β particles. β radiation consists of electrons or positrons, which are emitted during the decay process. This type of radiation is commonly observed with radioiodines. Option B is incorrect because γ radiation is a type of electromagnetic radiation emitted by the nucleus, not by radioiodines in this case. Option C is incorrect because radioiodines predominantly emit β radiation, not an equal amount of β and γ. Option D is incorrect because radioiodines do emit radiation, particularly β radiation, and therefore are not completely safe in terms of radiation exposure.

Correct Answer: A

Rationale: The correct answer is A: Granules in mast cells or basophils. Mast cells and basophils are well-known for storing histamine in their granules. Upon stimulation, these cells release histamine into the surrounding tissues. Histaminergic neurons (choice B) primarily release histamine in the brain and are not the main reservoir of tissue histamine. Enterochromaffin-like cells (choice C) are found in the stomach and release histamine into the bloodstream, not sequestering it in tissues. Therefore, the correct choice is A as most tissue histamine is indeed sequestered and bound in granules in mast cells or basophils.

Correct Answer: D

Rationale: The correct answer is D: Vitamin B1. This is a water-soluble vitamin, also known as thiamine. Water-soluble vitamins dissolve in water and are not stored in the body, so they need to be consumed regularly. Vitamin A (choice A), Vitamin E (choice B), and Vitamin D (choice C) are fat-soluble vitamins, meaning they are stored in the body's fat tissues and liver, not excreted in urine like water-soluble vitamins. Therefore, they are not water-soluble vitamins. Vitamin B1 (choice D) is crucial for energy metabolism and nerve function, making it a water-soluble vitamin that needs to be replenished regularly through diet.

Correct Answer: D

Rationale: The correct answer is D. This is because all three statements A, B, and C are true regarding nutritional supplements. A: Nutritional supplements are intended to supplement the diet and contain dietary ingredients like vitamins, minerals, herbs, amino acids, etc. B: Nutritional supplements are regulated as foods by the FDA, not drugs. C: Nutritional supplements do not require pre-approval for safety and efficacy, unlike drugs. Therefore, all of the statements are true, making option D the correct answer.

Correct Answer: D

Rationale: The correct answer is D: Probucol (Lorelco). Probucol decreases blood levels of HDL by inhibiting the enzyme that helps in the production of HDL. Lovastatin (A) works by lowering LDL levels, Nicotinic acid (B) increases HDL levels, and Gemfibrozil (C) works mainly on triglycerides and raises HDL levels. Probucol (D) is specifically known for lowering HDL levels.