I wanted to do volunteer work in mountainous areas. My mother thought it would be dangerous.

A. I wanted to do volunteer work in mountainous areas, but my mother thought it would be dangerous.

B. I wanted to do volunteer work in mountainous areas, so my mother thought it would be dangerous.

C. I wanted to do volunteer work in mountainous areas, because my mother thought it would be dangerous.

D. I wanted to do volunteer work in mountainous areas, and my mother thought it would be dangerous.