采用机车运输，列车或单独机车都必须前有什么？后有什么？
参考答案：
前有照明，后有红灯。
— Don't you think Jim was brave to go bungee jumping?
— Personally, I thought he was ________ brave. [ ]
A. more mad than
B. as mad as
C. mad more than
D. too mad as
管路发生泄漏的原因通常有哪几种？
