麻烦解答GWD中的一道语法题

是GWD中的一道题，不算难题，但是我没有想明白为什么。请大家帮忙看看。答案说是A，但是我觉得应该是B。麻烦高人指点

Q2: PP68.  

The cottontail rabbit population in Orange County, California, has increased unchecked in recent years as a result of the removal of the native fox population and the clearing of surrounding woodlands.

1. years as a result of the removal of

2. years as a result of removing

3. years, resulting from the removing of

4. years, which is result of removing

5. years, which is a result of the removal of