A few biology questions

Specific immunity is dependent on:
a. erythrocytes
b. thrombocytes
c. granulocytes
d. agranulocytes

A type of iron deficiency anemia is:
a. aplastic anemia
b. pernicious anemia
c. sideropenia
d. sickle cell anemia

and

A deficiency of clotting cell is:
a. purpura
b. leukopenia
c. polycythemia vera
d. thrombocytopenia

Plz, if you can explain. I want to be able to understand how you got the answer, to learn more instead of just asking questions. Thanks.

C. Granulocytes (Consists of specific antigen acting cells)
C. Sideropenia (A is megoblastic, B is error in bone marrow, D is hemoblastic)
D. Thrombocytopenia (Thromo means platlets - that aid in clotting)