在起重机上应用较广的为（）钢丝绳。
A.混绕捻
B.同向捻
C.交互捻
参考答案：C
已知x＞0，y＞0，x+3y+xy=9，则x+3y的最小值为______．
—Can you get me a ticket for the match？
—__________.[ ]
A. Sorry, no problem
B. Certainly, no problem
C. Excuse me, I can't
D. Certainly, not problem
