The primary immune response .

a. has a lag period while B cells proliferate and differentiate into plasma cells
b. occurs when memory cells are stimulated
c. occurs more rapidly and is stronger than the secondary response
d. is another name for immunological memory

a. has a lag period while B cells proliferate and differentiate into plasma cells

Explanation:

When the body comes in contact with foreign antigen for first time it is accompanied by primary immune responses, a lag period occurs in which no antibody is produced but activated B cells are transformed into plasma cells, this is called lag phase. The lag period may be as short as 2-3 days but is sometimes longer.

white blood cells consist of B cells which are formed in the bone marrow. Growing B cell (after first exposure) produces several copies of one type of antigens as a surface antigen receptor. The entire population of B cells has the ability to directly bind to millions of different antigens. If the antibody on a B cell's surface bind to an antigen, the cell will be primed to undergo proliferation and differentiation.

Hence, the correct option is a.

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b.have there own function.