Which of the two types of immu-
nity requires white blood cells?
explain.

The acquired or adaptive immunity requires white blood cells.

Explanation:

Acquired immunity acts by destroying the foreign particles with the help of white blood cell called lymphocytes. The lymphocytes – T cells and B cells activates the acquired immunity system.  

The T-cells activates mediated immunity, where they directly destruct the problematic cells like tumor cells. This cell-mediated action is proceeded by different T cells – cytotoxic, suppressor, and helper T cells.  

The B-cells activate humoral immunity by triggering antibody production against specific antigens and by signaling T cell activation. This antibody-mediated action is undertaken by plasma and memory B cells .

the answer is d. chordata

in 1859, charles darwin set out his theory of evolution by natural selection as an explanation for adaptation and speciation. he defined natural selection as the "principle by which each slight variation [of a trait], if useful, is preserved".