Today the forests are getting fewer and fewer. We must down too many trees.A. keep people

问题补充：

Today the forests are getting fewer and fewer. We must down too many trees.

A. keep people from cutting

B. prevent people from cutting

C. stop people cutting

D. all the above

答案：

A. keep people from cutting

B. prevent people from cutting

C. stop people cutting

(答案→)D. all the above

解析：选项ABD都是阻止人们砍掉的含义，根据上文，现在森林变得越来越少，可知选D。