The expanded form of DDT is:
a. dichloro diphenyl trichloroethane
b. dichloro diethyl trichloroethane
c. dichloro dipyridyl trichloroethane
d. dichloro diphenyl tetrachloroacetate
The answer is the option (a) dichloro diphenyl trichloroethane
Explanation: The full form of DDT is dichloro diphenyl trichloroethane according to its structural formula. Hence, (a) is the correct option.