They have not spoken to each other since they quarrelled.

Options

A. (1) for
B. (2) because
C. (3) ever since
D. (4) No Improvement

Answer

C

Explanation

ever since (Conj.) : continuously since the time mentioned
She had been worrying ever since the letter arrived. since (Conj.) : from an event in the past until now
t.s twenty years since I.ve seen her. Here, ever since is the right usage