Question

Which word in the sentence should be followed by a semicolon?
The girls were talking in a group quietly then someone interrupted.

a. group
b. quietly
c. talking
d. then
b?

Answer 1

 Semicolons are used in-between two main clauses and make a complete sentences.
If it were to be placed after group, talking, then it also wouldn't make a sentence, So you're right. The answer is B.