I think question and answer both are correct. because if you people see the question read it carefully,
"How many types of DML triggers in SQL are present? (DML - Data Modification Language)"
The question says that How many types of DML Triggers ok, its not asking how many type of triggers, its asking about DML Triggers,
So the answer is AFTER and INSTEAD of trigger.
But tell you the intresting thing that i have also ticked the 2nd option that is
3 types (DML triggers, DDL triggers and Logon triggers)
But if u'll read the question carefully then the question and answer both are correct.