How many crypto map sets can you apply to a router interface?

How many crypto map sets can you apply to a router interface?
A . 3
B . 2
C . 4
D . 1

Answer: D

Explanation:

You must assign a crypto map set to an interface before that interface can provide IPSec services. Only one crypto map set can be assigned to an interface. If multiple crypto map entries have the same map-name but a different seq-num, they are considered to be part of the same set and will all be applied to the interface.

Source: http://www.cisco.com/c/en/us/td/docs/ios/12_2/security/command