工作场所一氧化碳含量大于30mg/m3但不超过50mg/m3时，连续工作时间不应超过（）h。
A、1.5
B、1
C、0.5
参考答案：B
We should go to school by bus or underground rather than by car global warming.
A．reducing
B．to reduce
C．reduced
D．having reduced
