Answer:
A. Using a username and hashed version of password
Step-by-step explanation:
SNMP v2 allows password hashing with MD5, unlike the early versions SNMP v1 which sends passwords in clear-text over the network which allows packet sniffing to read the password, but the password hashing has to be configure n SNMP v2.
Therefore using a username and hashed version of a password would be most accurately describes how the SNMP agent on a router authenticates any SNMP Get requests received from the NMS.