Which of the following heart valves separates the right atrium from the right ventricle?

A. Natural passive immunity occurs when antibodies are passed from mother to child, either during pregnancy or through breast milk. This is not related to having the disease.

B. Artificial passive immunity is the transfer of antibodies from an external source, such as through antibody-containing blood products, to provide immediate protection against a disease.

C. Natural active immunity is acquired when an individual is exposed to a pathogen and the immune system responds by producing antibodies and memory cells. This type of immunity occurs after contracting the disease.

D. Artificial active immunity is gained through vaccination, where a person is exposed to a harmless form of the pathogen (such as inactivated or attenuated form), prompting the immune system to create a defense without causing illness.

A. The thyroid gland functions only as an endocrine gland. It secretes hormones like thyroxine (T4) and triiodothyronine (T3) into the bloodstream, but it does not have an exocrine function.

B. The pituitary gland is an endocrine gland that secretes hormones into the bloodstream but does not have exocrine functions.

C. The hypothalamus is involved in hormone production and regulation but is considered part of the brain rather than an endocrine or exocrine gland itself.

D. The pancreas functions as both an endocrine and exocrine gland. It produces insulin and glucagon (endocrine functions) and secretes digestive enzymes into the small intestine through ducts (exocrine function).