The correct option is B Blood of man
Gametocytes are formed in the human host by the when the protozoa shift from the asexual replication in erythrocytes. The precursors of male and female gametes, of malarial parasites, are picked up by the protozoa from the blood of an infected host and it activated in the salivary glands of the female Anopheles.
So, the correct answer is option A.