1. In summer my brother will have been travelling in the East for a year. (mu brother = he; he will)
2. Cats always run after the mice. (Cats - множ. число, а глагол runs стоит в форме ед. числа)
3. Douglas was running in the city marathon when I saw him. (were только для множ. числа)
4. The eagle was flying in the sky yesterday. (yesterday указывает на время)
5. The children are going to leave for the summer camp tomorrow. (children - множ. число)
6. Jane will be sitting at the lecture at this time tomorrow. (Future Continuous образуется при глагола be и причастия наст. времени (глагол с окончанием -ing)
7. My brothers are fighting now. I want to stop them. (ошибка в согласовании подлежащего во множ. числе и сказуемого в ед. ч.)
8. Ruth has washed all the linen. (Ruth = she; she has)
9. McFarland had cashed his cheques yesterday before he left. - верно
10. The married couple will have visited five countries by the end of their honeymoon. (the couple = they; they will)
11. Your kitten has been mewing for twenty minutes. What's wrong with it?
12. Jamie had been playing for three hours before we came in. (Past Perfect Continuous образуется так: had + been + V ing)
13. Next year Susan will have been working here for ten years. (Future Perfect Continuous)
14. Trevor plants cucumbers and roses every year. (Trevor = he; he plants)
15. His dog barked all night yesterday. (если barked, то должно быть обстоятельство, указывающее на время)