True or False: Vaccines can cause autism in children.

Explanation: Vaccinations are made from either weakened or killed pathogens or parts of pathogens, which cannot cause the disease they are meant to protect against. However, they stimulate the body's immune system to produce a protective response, providing immunity against the specific disease.

Explanation: The primary role of B cells during the humoral immune response is to produce antibodies against specific antigens on pathogens. When B cells encounter an antigen that matches their specific receptor, they become activated and differentiate into plasma cells, which then secrete large amounts of antibodies into the bloodstream.

Incorrect choices:

a. Antigen presentation to B cells is carried out by antigen-presenting cells, such as macrophages and dendritic cells, not by B cells themselves.

c. Directly attacking and killing infected cells is the role of cytotoxic T cells during cell-mediated immunity, not B cells during the humoral immune response.

d. The regulation of the immune response is mainly the function of regulatory T cells (Tregs) and other immune regulatory mechanisms, not the primary role of B cells.