Vasodilation causes:.

Choice A rationale:

Peyer’s patches are lymphoid nodules located in the small intestine and play a role in immune surveillance of the intestinal lumen and in the facilitation of the immune response.

Choice B rationale:

The appendix serves as a reservoir for beneficial gut bacteria. It is a narrow pouch that projects off the cecum in the digestive system.

Choice C rationale:

Adenoids are not known to serve as a reservoir for beneficial gut bacteria. They are located in the upper part of the throat and are part of the immune system, helping to fight off infections and trap bacteria that enter through the nose.

Choice D rationale:

Tonsils are not known to serve as a reservoir for beneficial gut bacteria. They are lymphoid tissues located at the back of the throat and help protect the body from respiratory infections.

Naturally acquired active immunity occurs when the body produces antibodies in response to an infection or vaccine. This is not the case for antibodies passed through the placenta.

Choice B rationale:

Artificially acquired passive immunity involves the injection of antibodies, not the transfer through the placenta.

Choice C rationale:

Innate immunity refers to nonspecific defense mechanisms that come into play immediately or within hours of an antigen’s appearance in the body. This does not describe the process of antibody transfer through the placenta.

Choice D rationale:

Natural passive immunity occurs when antibodies are passed from the mother to the fetus through the placenta. This matches the description in the question.

So, the correct answer is Choice D, after analyzing all choices.