Someone_____the door at midnight yesterday. D. are knocking B. were knocking C. is knocking A. was knocking

Someone_____the door at midnight yesterday.
D. are knocking
B. were knocking
C. is knocking
A. was knocking
Chọn câu D bởi vì nó có yesterday là dấu hiệu của thì HTTD và someone là số ít cho nên dùng is knocking 
Cấu trúc HTTD:  
S + am/are/is + Ving

Someone_____the door at midnight yesterday.

D. are knocking

B. were knocking

C. is knocking

A. was knocking

`->` at midnight yesterday `->` dấu hiệu QKTD

`->` someone `->` chủ ngữ số ít `->` dùng was

`banthamkhao`