Most of us enjoy fishing, swimming and ________ on the beach, and scientists and students have endless opportunities to study ________ life in the habit．

1. A.
   have fun; a lot of
2. B.
   having fun; a lot of
3. C.
   having fun; a variety of
4. D.
   have fun; a variety of

 Most of us enjoy fishing, swimming and ____ on the beach, and scientists and students have endless opportunities to study ____ life in the habitat.

   A. have fun, a lot of                 B. having fun, a lot of  

C. having fun, a variety of            D. have fun, a variety of

根据课文内容填空

Estuaries are also important because they 1 nutrients and pollutants from water coming 2 sources, thus cleaning our water. Unfortunately, this function also makes estuaries very 3 to environmental pollution. Since estuaries 4 animals and plants from storms and floods and 5 erosion. Protecting them is very important. Finally, estuaries 6 both recreation and 7 for human beings. Most of us enjoy fishing, swimming and having 8 on the beach, and scientists and students have 9 opportunities to study a variety of life in the habitat. Estuaries also 10 to the economy through tourism and fishing.