Most expenditures to combat such vector-borne diseases
like malaria and rabies have focused either on the immunization of humans or on obliterating the carriers with pesticides. A like malaria and rabies have focused either on the immunization of humans or on obliterating
(Incorrect) As is used to introduce examples, Like can only be used when we are implying similar behaviour ... Also, here a complex gerund is made parallel to simple gerund which isn't possible
B like malaria and dengue have focused either on immunization of humans or on the obliteration of
(Incorrect) Again Like has been used ..
C as malaria and dengue have focused on either immunizing humans or on obliterating
(incorrect) Incorrect usage of either .. or .. it should be either X or Y rather than either X or on Y
D as malaria and dengue have focused on either immunizing of humans or on obliteration of
(Incorrect) Here complex gerunds are parallel but the correct form should be immunization of humans ...
E as malaria and dengue have focused on either immunizing humans or obliterating
(Correct) Two gerunds are parallel in correct form .. correct usage of either or ...