The northern parts of the United States get very cold in the winter. It snows a great deal and the temperature often goes(21)zero degree in January,(22)and March. But the northeastern and northcentral regions of(23)have been financial and industrial centers, and they are heavily polluted.
In recent years,people in these regions have begun to take vacations(24)these cold winter months. They go to southern parts of the country(25)it is warmer. Many go to Florida where the weather is (26). Others go to the southwestern states of Arizona, New Mexico and Texas where they(27)dry desert climates.
It has become(28)nowadays for old people to move south to these places(29) they retire. Typically these people sell their houses in their home communities and move south to begin a new life(30)senior citizens.
Their children likely have homes(31)and many of them are moving south(32) communities where they were(33).The southern and southwestern parts of the country are now growing(34)any other part. Business and industry(35)many offices and factories in the south. California is already the most popular state in the country.
1. 第(31)题选（）
Aof their
Bof their own
Cfor theirs
Dfor their
2. I'd like to live somewhere_____the sun shines all year long.
Awhich
Bof which
Cwhere
Dat where
3. Young（）he is,he knows what is the right thing to do.
Athat
Bas
Calthough
Dhowever
4. He decided to devote all his time and effort（）scientific investigation.
