桥吊重大件业，风速应不大于每秒（）米。
A、14
B、15
C、16
D、17
参考答案：B
如果焊丝直径过粗，焊丝加热时间增加，使焊件过热就会扩大热影响区，同时导致焊缝产生（）缺陷。
He looks younger ______ his friend; in fact, he is three years senior _______ his friend.
A．to; to
B．than; by
C．than; than
D．than; to
