Which of the following best describes eosinophils?

Correct Answer: C

Rationale: Eosinophils are best described as a type of granulocyte found under mucous membranes that defends against multicellular parasites. They release toxic substances to combat parasitic infections and play a significant role in allergic reactions and asthma. Histamine secretion to stimulate inflammation is more characteristic of basophils, while high phagocytic activity and aggressiveness are features of neutrophils, not eosinophils. Describing eosinophils as the most abundant type of white blood cell that secretes toxic substances to pathogens is inaccurate since eosinophils specifically target multicellular parasites, not a broad range of pathogens.

Correct Answer: B

Rationale: When an A heterozygote individual (IAi) and an O individual (ii) have a child, there are four possible combinations of alleles that the child can inherit: IA from the A parent and i from the O parent; IA from the A parent and i from the O parent; i from the A parent and i from the O parent; i from the A parent and i from the O parent. Out of these combinations, 50% of the offspring will inherit the A allele from the A parent, resulting in A blood type. Therefore, the correct answer is 50%. Choice A is incorrect because the probability is not 25%. Choice C is incorrect as it overestimates the likelihood. Choice D is incorrect as it suggests a certainty which is not the case in genetics.

Correct Answer: B

Rationale: To prepare 250 mL of a 50 M solution of HCl, the formula V1 x C1 = V2 x C2 is used, where V1 is the volume of the stock solution, C1 is the concentration of the stock solution, V2 is the final volume of the desired solution, and C2 is the final concentration of the desired solution. Given V1 x 0 M = 250 mL x 50 M, solving for V1 results in V1 = (250 mL x 50 M) / 0 M = 32 mL. Therefore, 32 mL of the 0 M stock solution of HCl needs to be added to water to create a 250 mL solution of 50 M HCl. Choices A, C, and D are incorrect because they do not represent the accurate volume required for the dilution calculation based on the given concentrations and volumes in the problem.

Correct Answer: B

Rationale: The correct answer is 'Nephrons.' Nephrons are the structural and functional units of the kidneys responsible for creating and transporting urine. Each kidney contains thousands of nephrons located in the cortex and medulla. The nephron consists of the renal corpuscle, which includes the glomerulus, and the renal tubule, which consists of the proximal tubule, loops of Henle, and distal tubule. While the glomerulus, loops of Henle, and distal tubules are all parts of the nephron, the nephrons as a whole are specifically responsible for creating and transporting urine.

Correct Answer: D

Rationale: Thyroid hormone is the correct answer as it is primarily responsible for regulating metabolism. It plays a crucial role in controlling the body's metabolic rate, affecting how the body uses energy from food. Thyroid hormone levels can influence metabolism, energy production, and body weight regulation. Insulin, choice A, is involved in regulating blood sugar levels, not directly metabolism. Testosterone, choice B, is a sex hormone that primarily affects the development of male reproductive tissues. Adrenaline, choice C, is involved in the fight-or-flight response and not primarily responsible for regulating metabolism.