疲劳断口一般有三个区域,即疲劳源、疲劳裂纹扩展区和最后瞬时()。
参考答案:断裂区
—Danny, I can't stop playing computer games.
—For your health, I'm afraid you .[ ]
A. can
B. may
C. could
D. have to
The employee proved ___________ to the job and the boss praised him.
A.suitable
B.adequate
C.fit
D.useful