Correct Answer: C

Rationale: When GABA binds with a receptor site, it causes hyperpolarization of the local nerve membrane, making it less excitable. This hyperpolarization leads to inhibition of nerve cell activity. Choice A is incorrect because GABA is a neurotransmitter itself and does not require three chemical substances to stimulate activity between cells. Choice B is incorrect as GABA triggers inhibitory postsynaptic potentials (IPSPs), leading to hyperpolarization, not depolarization, of the postsynaptic membrane. Choice D is also incorrect as it describes a process involving cholinergic receptors and acetylcholine, which is unrelated to GABA's mechanism of action.

Correct Answer: C

Rationale: When GABA binds with a receptor site, it causes hyperpolarization of the local nerve membrane, making it less excitable. This hyperpolarization leads to inhibition of nerve cell activity. Choice A is incorrect because GABA is a neurotransmitter itself and does not require three chemical substances to stimulate activity between cells. Choice B is incorrect as GABA triggers inhibitory postsynaptic potentials (IPSPs), leading to hyperpolarization, not depolarization, of the postsynaptic membrane. Choice D is also incorrect as it describes a process involving cholinergic receptors and acetylcholine, which is unrelated to GABA's mechanism of action.

Correct Answer: A

Rationale: The correct answer is A. Raloxifene works by decreasing bone resorption and increasing bone density. This helps in preventing further bone loss and reducing the risk of fractures in patients with osteoporosis. Choice B is incorrect because raloxifene does not stimulate the formation of new bone, but rather helps to maintain existing bone mass. Choice C is incorrect as raloxifene does not directly increase calcium absorption in the intestines. Choice D is also incorrect as raloxifene does not increase the excretion of calcium through the kidneys.

Correct Answer: B

Rationale: In this scenario, where impaired erythropoiesis is suspected, the most clinically relevant laboratory studies would focus on red blood cell parameters. Therefore, assessing RBC count, hemoglobin levels, and hematocrit values would provide direct insights into erythropoiesis. Choices A, C, and D are not directly related to erythropoiesis assessment. White blood cell count with a differential is more indicative of immune response and infection. INR and aPTT are coagulation studies, while d-dimer and C-reactive protein levels are more associated with inflammation and thrombotic events.

Correct Answer: A

Rationale: The correct answer is A: Cough and fever. After receiving the MMR vaccine, some children may experience mild adverse effects such as a low-grade fever and a mild cough. These symptoms are normal reactions to the vaccine and indicate that the child's immune system is responding appropriately. Choices B, C, and D are incorrect because pallor and listlessness, serum sickness, nausea, and vomiting are not common adverse effects associated with the MMR vaccine in children.