氢脆性
参考答案：
氢脆性指氢引起的钢的塑性严重下降的现象。
--- After school, let’s go to play football together.
--- OK.________.
A. that’s settled B. You are welcome C It’s up to you. D. After you.
小儿最常见的尿路感染途径是（）
A．逆行感染
B．血源性感染
C．淋巴感染
D．邻近组织浸润
E．外伤
