Ребят, помогите, кто может) Какое правило тут надо использовать? В принципе. решение присылать не обязательно, хотябы правилоооо^^

Open the brackets and use the correct form.

1. My friend was sure that Ferdinand Magellan (discovered, had discovered) Australia. But I told him he (is, was) wrong. 2. Our history teacher explained to us that the Revolutionary War in America (took, had taken) place in the 18th centry.3. Betty knew that she(did, had done) everything she could to win the competition.4. We asked Professor Smith when he(came, had come) to Moscow how many places of interest he already(saw, had seen). 5. Little JOHN delieved that Canada (is,was) in the South of the American Continent. 6. We all wanted to know where in New York the Statue of Liberty (is,was) situated. 7. The children asked what cities in the  USA we (saw, had seen) . 8. Father told me that I (made, had made)a mistake in my school test. 9. We all knew that Germany (declared, had declared) war on several European countries in 1941. 10. He said he always (supported, had supported) me. 11.Not all the pupils kneww that the US President (is,was) the Commander in Chief of the countrys armed forces.