Vaccinations are effective in combating future infections because they induce the production of:
a. t cells
b. neutrophils
c. prostaglandins
d. mutations in the host
d. memory cells

a. Helper T cells

Explanation:

Vaccines help develop immunity by imitating an infection. This

type of infection, however, almost never causes illness, but it

does cause the immune system to produce T-lymphocytes and antibodies.

mammal

explanation:

if your own plato the answer is b. the fern transitioned from sporophyte generation to gametophyte generation.