WE HAVEN'T KEPT IN TOUCH WITH EACH OTHER ……… .A. SINCE 6 DAYS B. F...

64. - BAI TAP TRAC NGHIEM TONG HOP A9
BAI TAP TRAC NGHIEM TONG HOP A9

64. We haven't kept in touch with each other

……… .

a. since 6 days b. for 6 days c. 6 days

ago d. over 6 days