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有效
D．要约人虽表示接受也无效
参考答案：C
Some researchers believe that many patterns of nature are rules of their own and not affected by natural selection．
A．making
B．breaking
C．following
D．bending
甲土的饱和度大于乙土的饱和度,则甲土的含水量一定高于乙土的含水量.
