按《招标投标法》规定，招标文件自发放之日起，至投标截止时间的期限，最短不得少于（）天。
A.15
B.20
C.30
D.45
参考答案：B
一测量船将超声波垂直向海底发射，测出从发射超声波到接收反射波所用时间是4s，已知声音在水中传播速度1500m/s．问：此处海底深度是多少？
Unfortunately, George cannot be with us today so I am pleased to accept this award____ him.
A．in honor of
B．instead of
C．on behalf of
D．for lack of
