Which choice contains a prepositional phrase within a dependent clause?

Responses
A We went to the concert, so we aren't miserable.We went to the concert, so we aren't miserable.
B If we don't go to the concert, we will be miserable.If we don't go to the concert, we will be miserable.
C You didn't go to the concert? You must be miserable.You didn't go to the concert? You must be miserable.
D Let's go to the concert, so we don't become miserable.

B If we don't go to the concert, we will be miserable.