Birds are fascinating to many people, and bird watching is a popular hobby. The best time to watch birds is in the early morning, (1)_____ birds are usually very active at that time of the day. The obsever must keep still and quiet in order not to (2)_____ the birds away. If you live in a part of the world where migratory birds spend their breeding season, then you will have the (3)_____ to see nest-building activity. It makes an interesting study to (4)_____ the different types of nests built by birds and to watch them as they built their nests. After the breeding season is over and the babies have left the nest, it is time for the birds to head for (5)_____ parts of the world to spend the winter months. Birds navigate to their winter feeding ground, using the stars or the sun as their guide.
1. A. so B. because C. though D. but
2. A. upset B. throw C. frighten D. worry
3. A. time B. prospect C. occasion D. opportunity
4. A. look at B. take after C. care for D. see off
5. A. warmer B. cooler C. hotter D. colder