Question 16: The doorbell ________________ while I ________________ a

Question 16: The doorbell ________________ while I ________________ a shower.

• A. was ringing – took
• B. rang – was taking
• C. had rung – took
• D. had been ringing – took

S + V (quá khứ đơn) + while + S+ V (quá khứ tiếp diễn).