郭沫若在《中国古代社会研究》一书中，在中国历史研究上第一次提出（）的问题。
查看答案
汽车散热器格栅可能安装在（）之上。
A. 保险杠
B. 前面板或散热器支架
C. 发动机舱盖
D. 以上全部
You are carrying cargoes of crotonaldehyde，phosphoric acid，and morpholine on your multiple-product tanker. Which of the following statements is TRUE? （）
A. Each of the cargoes must be segregated from the other by at least two barriers
B. The minimum protective clothing required for taking samples of phosphoric acid is goggles or a face shield
C. Aluminum，copper，and zinc are prohibited in all valve parts in contact with these cargoes
D. The required warning sign must have the legend "cancer hazard" added to it
微信支付 
支付宝支付