2012年末统计，杭州市常住人口是880.2万人，用科学记数法表示为       .

There was no sign _______ they had died from diseases such as bird flu - the main worry in such cases. Among the theories was _______ a truck had collided（碰撞）with the crowd.  

A．/; that

B．that; that

C．that; which

D．that; /