Correct Answer: A

Rationale: The correct answer is A: Blood. IgA1 is mainly found in the blood and plays a crucial role in preventing infections by neutralizing pathogens. While IgA1 can be present in other body areas, its primary function is associated with preventing infections in the blood. Choices B, C, and D are incorrect as IgA1 is not primarily associated with the kidneys, lungs, or mucous membranes.

Correct Answer: C

Rationale: Ivermectin (Stromectol) is commonly used to treat parasitic infections, particularly Strongyloides stercoralis. This parasitic infection is known to respond well to Ivermectin therapy. Entamoeba histolytica causes amoebiasis and is typically treated with antiprotozoal drugs like metronidazole, not Ivermectin. Giardia lamblia is a protozoan parasite causing giardiasis, which is usually treated with medications like metronidazole or tinidazole, not Ivermectin. Plasmodium falciparum is a malaria-causing parasite and is not treated with Ivermectin but with antimalarial medications like chloroquine or artemisinin-based combination therapies.

Correct Answer: C

Rationale: The correct answer is to use the Wong-Baker FACES scale to assess the child's pain. This scale is specifically designed for children and uses facial expressions of varying intensities to help them communicate their pain levels effectively. Choices A and B may not be as suitable for a young child who may have difficulty understanding or using a numerical scale. Choice D involving parents may not provide an accurate reflection of the child's pain experience, as it is essential to assess the child's self-reporting.

Correct Answer: B

Rationale: Acetylcholine acts as an inhibitory neurotransmitter at the sinoatrial node. It slows down the heart rate by decreasing the firing rate of the sinoatrial node, which serves as the heart's natural pacemaker. Neurotransmitters do not have a charge, so choice A is incorrect. Choice C is wrong as overstimulation is not a characteristic of acetylcholine at the sinoatrial node. Choice D is also incorrect because acetylcholine actively influences heart rate regulation when released at the sinoatrial node.

Correct Answer: A

Rationale: Antibodies are produced by B cells. B cells are specialized white blood cells that generate antibodies as part of the immune response. B cells differentiate into plasma cells that secrete antibodies. T cells play a role in cell-mediated immunity, not antibody production. Helper cells, or helper T cells, assist in activating B cells but do not directly produce antibodies. Memory cells store information about previous infections but do not actively produce antibodies.