How is the word "thronged" used in the following sentence? Must explain why, it is correct.

"A feeling of despair began to take possession of him; all the more as the streets became more thronged and the merchants began to open their shops."

 

A.
As a synonym for despair
 

B.
As something that happened in the past
 

C.
As a verb to describe what's happening in the streets
 

D.
As a plural noun like merchants