Answer:
1. We live in a sunny country. (present tense)
2. They solved an important problem last week. (past tense)
3. –What you are doing now? – I am looking for my book.(present continuous tense)
4. This book had been written 5 years ago. (past perfect tense)
5. This letter have written just now.(present perfect tense)
6. Our friend speaks two foreign languages. (present tense)
7. A new directory had been printed from 2 to 4 p.m. yesterday.(past perfect continuous tense)
8. Jack built a house by June.(past tense)
9. You understood a rule yesterday?(past tense)
10. This rule had been explained by our teacher.(past perfect continuous tense)
