Which security mechanism is responsible for verifying that users are indeed who the claim to be?

A.
Authentication

B.
Roles and privileges

C.
Mandatory access control

D.
Discretionary access control

Explanation:
https://www.ibm.com/support/knowledgecenter/en/SSEPGG_9.7.0/
com.ibm.db2.luw.admin.sec.doc/doc/c0005435.html