GWD 23-31

s搜了一下没有以前的讨论。

Q31:

According to some botanists, invasive plants are the second most serious threat, after habitat loss, to native species of plants and animals and to the maintenance of biologically diverse ecosystems.

1. threat, after habitat loss, to native species of plants and animals and to the maintenance of biologically diverse ecosystems

2. threat, after habitat loss, to native species of plants and animals and for maintaining biologically diverse ecosystems

3. threat, after losing their habitat, to native species of plants and animals and also to maintenance of biologically diverse ecosystems

4. threat to native species of plants and animals and for maintaining biologically diverse ecosystems, after habitat loss

5. threat to native species of plants and animals as well as to maintaining biologically diverse ecosystems, after losing their habitat

   Answer:  A

why not B, 现在分词更能体现对动作的威胁。

期待nn指点