柴油机的机体由高强度（）制成，为隧道式结构。
A.碳钢
B.铸钢
C.合金钢
D.铸铁
参考答案：D
用所给单词的适当形式填空。
1. The boy is doing ______________ (he) homework.
2. How many ______________ (ticket) do you want to buy?
3. I am ______________ (tall) than my little brother.
4. Li Ming ______________ (have) two pairs of socks.
5. She is ______________ (get) ready for bed.
Can you think of some cases where drivers obviously______ the traffic rules but don’t obey them?
A．have instructed in
B．have instructed
C．have been instructed in
D．are instructed
