What is not true about Salmonella thyphimurium?

Correct Answer: A

Rationale: The correct answer is A: It is the causal agent of "hamburger disease." Salmonella typhimurium is not the causal agent of "hamburger disease." Instead, Escherichia coli O157:H7 is the primary causal agent of this particular foodborne illness. Salmonella typhimurium is commonly associated with causing salmonellosis. Therefore, choice A is incorrect. Choices B, C, and D are all true statements about Salmonella typhimurium. It is the second most common cause of food poisoning, it is able to induce its own uptake by manipulating the actin cytoskeleton of host cells, and it is able to survive inside the phagosomes by manipulating the host actin cytoskeleton.

Correct Answer: A

Rationale: The correct answer is A because naïve lymphocytes circulate through blood, enter lymph nodes (LN) via high endothelial venules (HEV), encounter antigens in LN, exit via efferent lymphatics, drain into the thoracic duct, and return to blood circulation. Choice B is incorrect because it skips the step of entering LN through HEV. Choice C is incorrect because it starts with inflammatory sites instead of blood, and it also lacks the step of entering LN through HEV. Choice D is incorrect as only option A correctly follows the sequential order of recirculation of naïve lymphocytes.

Correct Answer: D

Rationale: The correct answer is D because auxin hormones play a crucial role in promoting seedling elongation (A), are transported downward through a plant (B), and affect cell elongation in roots at lower concentrations (C). Auxins are known for their ability to stimulate cell growth and elongation, which is essential for seedling growth. They are also transported in a polar manner from the shoot tip downwards, influencing various plant processes along the way. Additionally, auxins regulate root growth by promoting cell elongation at lower concentrations. Therefore, all the statements (A, B, and C) are supported by the functions of auxin hormones, making option D the correct choice.

Correct Answer: B

Rationale: The correct answer is B: to vaccination. Acquired immunity is the immune response developed after exposure to a vaccine, which stimulates the immune system to recognize and remember specific pathogens. Vaccination helps the body build immunity without causing serious illness like choice A, without requiring repeated exposure like choice C, and without being related to treatment with penicillin like choice D. Vaccination mimics natural infection, prompting the body to produce memory cells that can respond more effectively when encountering the actual pathogen in the future.

Correct Answer: A

Rationale: The correct answer is A: Leukocytosis. Leukocytosis refers to an abnormal increase in white blood cells, indicating an immune response. Thrombocytosis (B) is an increase in platelets, not white blood cells. Anemia (C) is a decrease in red blood cells. Hemolysis (D) is the breakdown of red blood cells, not related to an increase in white blood cells. Therefore, A is the correct answer as it specifically relates to an abnormal increase in white blood cells.