[Ask ] Grammar questions

[mingtai1 (snake)]

My friends asked two grammar questions.. though I can pick up the correct
answers, I can't explain clearly why other answers are wrong
Here are the questions:
1.
____ a noise just then?
a.Have you heard
b.Did you hear
c.Were you hearing
d.Are you hearing

the answer is b ,but why not a or c

2.
Look! It's eleven o'clock. We ____the train.
a.just miss
b.had just missed
c.were just missing
d.have just missed
isn't it the past time?

the answer is d (why b is wrong? )

thanks a lot !

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→ bird6978:"just then" means it happened in the past, a,d are w
→ bird6978:wrong,in addition, u cannot be hearing a noise
→ bird6978:so c is wrong
→ bird6978:Q2, b is wrong because of "It's 11" . it means you
→ bird6978:are at 11, it's present tense. u have to choose d
→ bird6978:Time bar: miss train->now present prefect tense