某一同学刚开始养鱼时，用煮后晾凉的自来水给鱼换水，结果鱼都死了，原因是（）。后来在妈

Word came from Mr. Smith __________ he could arrive on the following Saturday.

A．where

B．that

C．whether

D．which

下列著名诗句中隐含化学变化的是

A．春蚕到死丝方尽，蜡炬成灰泪始干

B．只要工夫深，铁杵磨成针

C．千里冰封，万里雪飘

D．夜来风雨声，花落知多少

It is obvious to the students ________ they should get well prepared for their future.[ ]

A. as  

B. which  

C. whether  

D. that

高瓦斯矿井采煤工作面上隅角必须设臵什么瓦斯检测仪器？

增生性龈炎的临床表现是

A．探诊出血

B．龈缘肥厚

C．多发生于前牙的唇侧牙龈

D．可形成假性牙周袋

E．以上都是