What technique this user was trying?

Using Internet logging software to investigate a case of malicious use of computers, the investigator comes across some entries that appear odd.

From the log, the investigator can see where the person in question went on the Internet.
From the log, it appears that the user was manually typing in different user ID numbers.

What technique this user was trying?

A.
Parameter tampering

B.
Cross site scripting

C.
SQL injection

D.
Cookie Poisoning