Is it a participle clause?

I have just come across this question when doing senior high school English grammar question.

The former businessman has gone on trial _____ of two million dollar investment fraud.

a. accuse
b. accused
c. accusation
d. accusing

I would choose b option without a doubt but I couldn’t understand why there isn’t extra words like "for which he was" before accused? what is the grammar based on? or was I wrong from the start perhaps the better answer is not b?