Could you correct the using of the tense forms please?

1) When did she choose to take a course in English?
2) It was easy for him to get lost because he hadn't been in a big city before.
3) I had been reviewing grammar rules before the test when my computer started to [blink?].
4) I don't remember exactly how long ago it was.
5) Roger didn't give any explanation as to why he was late for school.
6) What were you doing at 10 o'clock yesterday morning?
7) We were late.When we arrived everyone had finished their lunch and they were sitting in the garden having coffee.
8) I ran to the station but the train had already left.The station was empty except for three people who were waiting for the next train.
9) They had been driving to the airport when they suddenly remembered that they didn't turn off the central heating.
10) The match had already started when we turned on the TV.Scotland lost 1:0 and they played very badly.