НАДО! 1)By the time Alexander was twenty he (become) a professional scientist.
2)When Alex (hang up) the phone he (realise) he (forget) to take down the caller’s name and number.
3)He (work) in the laboratory for three hours when he stopped for a break.
4) Alex (read) a book all night and was very sleepy the next morning.
5) They were exhausted because they (play) chess all day.
6) Before Fleming invented penicillin, he (experiment) with bacteria for a long time.
7) I (decide) that I was going to study Chemistry before I finished secondary school.
8) Alexander (already/learn) to read and write before he started school.
9) He was upset because he (miss) the last train.
10) He (reach) his house by the time it started to rain.
