Plasmodium is transmitted to humans by the bite of a mosquito (Anopheles). Its life cycle is characterized by spores, gametes, and cysts that can "hide" in human cells. This infective protist belongs to the group:
a. Apicomplexa.
b. Archaeplastida.
c. Dinoflagellata.
d. Oomycota.
e. Ciliophora.