对于受要约人延误的承诺，该承诺( )。

A．有效

B．无效

C．要约人未表示不接受，则有效

D．要约人虽表示接受也无效

Now that every thing is made clear, we ( )despatch next week by rail.

A．would

B．should

C．are arranging for

D．will be for