二、译成汉语无主句

Measures have been taken to prevent the epidemic from spreading quickly.  已经采取了措施来防止这种流行病迅速蔓延。

Water can be shown as containing impurities.  可以证明，水含有杂质。

The unpleasant noise must be immediately put an end.   必须全部停止这种讨厌的噪声。