有这样两个选择题.1、While watching television,________.A.the doorbell

有这样两个选择题.
1、While watching television,________.
A.the doorbell rang
B.the doorbell rings
C.we heard the doorbell ring
D.we heard the doorbell rings
我选的是D,但答案是C.为什么?
2、——Did Jack come back early last night?
——Yes.It was not yet eight o'colck_______ he arrived home.
A.before B.when C.that D.until
我选的是D,为什么?我明明记得有个句式是“it was not ...until.”的?