关于乐音和噪声的叙述中正确的是（   ） 

A．乐音是乐器发出的声音，噪声是机械发出的声音

B．乐音悦耳动听，使有心情舒畅，噪声使人烦躁不安，危害人体健康

C．从环境保护的角度看，一切干扰人们正常学习、工作的声音都叫噪声

D．乐音的振动有规律可循，噪声的振动杂乱无章无规律可循

It ______ we had stayed together for a couple of weeks ______ I found we had a lot in common.

A．was until; when

B．was not until; that

C．was not until; when

D．was until; that