天然气与液化石油气的着火温度相比，则（）。
A、天然低
B、液化石油气低
C、一样低
D、难以比较
参考答案：B
If he had spent more time practicing speaking English before, he _____ able to speak it much better now.
A．will be
B．would be
C．has been
D．would have been
（），不会直接造成小车打滑。
A、车轮倾斜
B、制动过猛
C、轨顶上有油污
