车门槛内的插入件长度一般是()。
A、10mm~20mm
B、15mm~30mm
C、20mm~30mm
参考答案:B
Instead of importing Chinese labor,the United States is importing goods that are produced with Chinese labor,which is a typical example of importing goods from another country instead of importing factors of production.( )
氧气瓶内氧气不能全部用完,最后要保持0.1-0.2MPa的压力。