глаголы в скобках поставить в нужную временную форму Past Simple или Past Continuous
1. The steam engine … (to appear) in 1763
2. I (not to go) out last night because it (to rain).
3. Mendeleev … (to create) his Periodic Table in 1871.
4. They (to come) in when I (to have dinner) with my friend.
5. Ecological problems … (to appear) in the XX century.

1) The steam engine appeared in 1763.2) I didn't go out last night because it was raining.3)  Mendeleev created his Periodic Table in 1871.4) They came in when I am having dinner with my friend. 5) Ecological problems appeared in the XX century.