We don’t have much homework now and our school bags are ____they used to be.  

A．as heavy as

B．not as heavy as

C．as heavily as

D．not as heavily as

目前流行的“非典型肺炎”是属于______传染病，它通过______传播．致病的病原体是______病毒，其临床表现主要有发烧、干咳、肺部有阴影、白细胞下降等．同学如有发烧等，请及时查明病因．因为正常的______是保证人体进行生命活动最重要条件之一．