Select the Answer That Joins Each Pair of Simple Sentences

Multiple Choice

Select the answer that joins each pair of simple sentences with conjunctions or conjunctive adverbs correctly and is punctuated correctly. I couldn't bring the clients both to and from the conference.
Betty offered to drive one way.

A) Betty offered to drive one way so I couldn't bring the clients both to and from the conference.
B) I couldn't bring the clients both to and from the conference, therefore Betty offered to drive one way.
C) Because I couldn't bring the clients both to and from the conference, Betty offered to drive one way.