When did you first know him?

=> How long ______?

Rivers are on of the world's most important natural resources. Many cities are on the large rivers, and (1) ______ every country has a least one river that (2)______  an important part in the lives of its people. Besides transportation, rivers (3)______ water for crops, water to drink, and recreation for people who live along their (4)______ And in (5)______  to get water for crops, engineers sometimes build a dam (6)______  a river and let water become a lake behind the dam. Then people can use their water not (7)______  to irrigate fields but also to make electricity for homes and industries. (8)______ the water often becomes polluted when cities on river bank grow (9)______  and the number of industries increases. We are learning that it is necessary to (10______ rivers clean if we want to enjoy the benefits of the natural resources.

Reading scientific books is one of my interests.

=> I'm ______.

Tìm lỗi sai: In contrast to my brother is hardworking, I am quite a lazy boy.

Villagers are more kind, friendly and warm-hearted than city _______.

She put ______ speaking to him as long as possible.