氢脆性
参考答案：
氢引起钢的塑性严重下降的现象。
---You aren’t looking well. Anything the matter?
---I’ve been surfing the net too long. I’m a bit tired.I can hold on,____.
A．though
B．yet
C．besides
D．therefore
假如你当导游，你能说出广西壮族自治区、海南省的哪些景点？
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