Hashing related question's

There is this question that is really bugging me.. It's on a test sim for CISSP..

Here is the question as it is:

What hashing algorithm is implimented by IPSec

Options:

MD5
SHA-1
HAVAL
HMAC..

The answer is HMAC !

HMAC isn't an algorithm ! its a type of MAC
Shouldn't SHA-1 be the answer ?

A Hash Message Authentication Code, is a type of message authentication "code" calculated using a specific algorithm that uses a cryptographic hash function in combination with a secret key. It verifies both the data integrity and the authenticity. Any iterative cryptographic hash function, such as MD5 or SHA-1, may be used to calc an HMAC. the resulting MAC is termed HMAC-MD5 or HMAC-SHA1 accordingly.

I surmise they are differentiating between the algo and various hash functions.

Thanks mate.. :)