IT HAS BEEN A LONG TIME _____ HE LAST TALKED TO HIS BEST FRIEND. A...

21. - TONG HOP BAI TAP VE TU LUAN TONG HOP BAI TAP VE TU LUAN
TONG HOP BAI TAP VE TU LUAN TONG HOP BAI TAP VE TU LUAN

21. It has been a long time _____ he last talked to his best friend.

A. ago

B. when

C. after

D. since