The structural basis of blood group A and B antigen specificity is

Correct Answer: A

Rationale: The correct answer is A: a single terminal sugar residue. Blood group A and B antigens are determined by the presence of specific sugar molecules at the terminal end of glycoproteins on red blood cells. The specificity is based on the addition of a single sugar residue - either N-acetylgalactosamine (A antigen) or galactose (B antigen) to the H antigen precursor. This single terminal sugar residue determines the blood group specificity. Choice B is incorrect because amino acids are not involved in determining blood group antigens. Choice C is incorrect as blood group antigens are determined by single sugar residues, not multiple differences in the carbohydrate portion. Choice D is incorrect as blood group antigens are based on sugar residues, not protein differences.

Correct Answer: B

Rationale: The correct answer is B: stimulating antibody production. Vaccinations introduce a weakened or inactive form of a pathogen to trigger the immune response. This leads to the production of specific antibodies that recognize and attack the pathogen upon future exposure. Antibodies play a crucial role in neutralizing and eliminating pathogens. A: Inhibiting antigen production is incorrect because vaccines aim to stimulate the immune system's response to antigens, not inhibit their production. C: Inhibiting white blood cell production is incorrect because white blood cells are vital components of the immune system and are not suppressed by vaccinations. D: Stimulating red blood cell production is incorrect because vaccinations do not have a direct impact on red blood cell production, which is primarily regulated by the body's own mechanisms.

Correct Answer: B

Rationale: The correct answer is B because Hepatitis A is transmitted through the fecal-oral route by consuming contaminated food or water. Stopping the consumption of raw clams, which could potentially be contaminated, is an appropriate precaution. A is incorrect as it mentions Hepatitis B transmission through shared needles and unclean tattoo equipment, which is not relevant to Hepatitis A. C is incorrect as avoiding all physical contact is an extreme measure and unnecessary for preventing Hepatitis A transmission. D is incorrect as boiling drinking water for 10 minutes is not a specific preventive measure for Hepatitis A, which is mainly spread through contaminated food and water.

Correct Answer: B

Rationale: Rationale: B is correct because HIV can be transmitted through contact with infected blood, with the highest concentration of the virus found in blood. Other body fluids like sputum, saliva, cerebrospinal fluid, urine, and semen can also contain the virus. Incorrect Choices: A is incorrect as HIV is not necessarily transmitted when symptoms manifest or during the asymptomatic period. C is incorrect as HIV can be transmitted through various routes, not just sexual contact. D is incorrect as HIV is not transmitted through airborne means.

Correct Answer: B

Rationale: The correct answer is B because wearing don clean gloves provides a barrier to prevent direct contact with bodily fluids contaminated with VRE. Gloves are essential in preventing the transmission of bacteria during care. Choice A is incorrect because goggles are not specifically necessary for VRE of the urine unless there is a risk of splashing or spraying of bodily fluids towards the eyes. Choice C is unnecessary unless there is a high risk of exposure to splashes or sprays to the face. Choice D is not necessary for all interactions unless there is a risk of contamination of clothing with bodily fluids.