给水铸铁管在使用前应检查管材有无裂缝和砂眼。检查时可用手锤轻敲管身，一般如发出清音说明没有问题，浊音和沙哑音即为不合格。
参考答案：对
根据句意和首字母提示补全单词。
1. Danny fell on top of Brian and Brian was i_____.
2. Our school has just worked out a new s_____ rule.
3. Mary just has a cold. Nothing s_____.
4. You must be more c_____ when you cross the road.
5. I'm not m_____ at you.
6. The a_____ happened at about 7:30 am.
7. I didn't go to bed until my mother r_____ last night.
8. After the accident, the driver called an a_____.
9. I wanted to s_____her from running after the ball.
10. A w_____ to the accident was walking behind the two students.
某研究人员模拟肺炎双球菌转化实验，进行了以下4个实验①S型菌的DNA+DNA酶→加入R型菌→注射小鼠②R型菌的DNA+DNA酶→加入S型菌→注射小鼠③R型菌+DNA酶→高温加热后冷却→加入S型菌的DNA→注射小鼠④S型菌+DNA酶→高温加热后冷却→加入R型菌的DNA→注射小鼠以上4个实验中小鼠存活的情况依次是（）
A.存活，存活，存活，死亡
B.存活，死亡，存活，死亡
C.死亡，死亡，存活，存活
D.存活，死亡，存活，存活
