Malignant malaria is caused by

All stages of Plasmodium are digested in stomach of female Anopheles except

$A$ : Vaccine against $AIDS$ has not been made inspite of repeated attempts.
$R$ : $HIV$ has the ability to get mutated to form several subtypes.

Antigen binding site in an antibody is formed by

Typhoid fever could be confirmed by

Which disease in children is caused by intensive use of nitrate fertiliser