The correct answer is C.
The verb to forge has several different meanings in the English language.
1. To make an illegal copy of something in order to deceive.
He forged his passport in order to enter the United States.
2. To make or produce something, especially with some difficulty.
It was not easy to forge a friendship with this shy boy.
3. To suddenly and quickly move forward.
She forged through the puddles.
To forge a friendship means to build it up steadily over a period of time.
