下列不属于要约失效的原因是( )
A.受要约人拒绝要约
B.要约有效期满,受要约人未做出承诺
C.受要约人对要约内容做出实质性变更
D.要约人依法撤回要约
参考答案:D
I can't go home now because I forgot _____ umbrella _____ me.[ ]
A. to bring; to
B. bringing; to
C. to take; with
D. taking; with
水体监测中挥发酚、甲醛、三氯乙醛、苯的测定需采用的方法是分光光度法。( )