温度低于-30℃的液氧输送应采用______、铝合金管。
参考答案:铜管
I am blue. Yesterday, I met a classmate in my new school, but when I stopped and smiled,
she ______me and walked on. [ ]
A. missed
B. refused
C. denied
D. ignored
车钩在使用中有哪几种状态?