超声波探伤的探头有哪几种形式？
参考答案：
直探头、斜探头、双晶探头、液侵探头。
---Have we ________ food?.
--- Yes, ______. We’d better buy some.
A．run out of; we have run it out
B．run out of; our food has run out
C．run out; our food has been run out
D．run out; our food has run out
The manager of the travel agency was trying hard to figure out how he would attract more customers ____ an extraordinary idea _____ his mind and he immediately knew what to do. [ ]
A. when; flashed across
B. as; crossed
C. when; hit
D. before; struck
