Which of these cancer drugs acts by adding hydrocarbon groups to dna? alkylating agents?

The propositions are:
a.alkylating agents
b.antimetabolites
c.topisomerase inhibitors
d.nucleoside analogs
e.AZT

The right answer is A, 
An alkylating agent is a compound capable of adding alkyl groups to various electronegative groups under conditions present within the cells.

Antimetabolites are an anticancer drug but act differently than the alkylating agent. (interfere with folic acid)
Topoisomerase inhibitor acts by inhibiting isomerase, used in antibiotherapy (like quinolones).
Nucleoside analogs are analogs as their name says, it does not alkylate nucleotides.
AZT (Zidovudine) is an antiretroviral drug that inhibits reverse transcriptase.