Which sentence uses abbreviations correctly?

A.
When I knew Don at UCLA, he wanted to work for the FBI.
B.
When I knew Don at UCLA, he wanted to work for the F. B.I.
C.
When I knew Don at UCLA, he wanted to work for the Federal Bureau of Investigation.
D.
When I knew Don at U. C.L. A, he wanted to work for the F. B.I.