道路运输大型气瓶时,车上必须配备防止钢瓶滚动的紧固装置,如插桩、垫木、紧绳器等。
参考答案:对
一I can't go to school today. I have a headache.
一_________[ ]
A. That's OK.
B. It doesn't matter.
C. I hope not.
D. I'm sorry to hear that.
猪在群体中的位次关系的形成是靠()
A、性别
B、年龄
C、毛色
D、争斗力