高温、高压下的氢对金属有( )，易造成氢腐蚀。
A．氧化作用 B．还原作用C．脱碳作用 D．硝化反应
参考答案：C
列方程解应用题
跑得快的马每天走250里，跑得慢的马每天走160里，慢马先走9天，快马几天可以追上慢马？
The number of the cranes is getting _____. If we don’t help them, they will disappear _____a few years [ ]
A. fewer and fewer, in
B. larger and larger, after
C. more and more, after
D. smaller and smaller, in
