承诺自（）时生效
A、通知到要约人
B、要约人签字
C、要约人到场
D、合同规定时
参考答案：A
To make believe that there was still someone in the house, the housewife went downstairs, ______ the lights ______ in the living room.
A．left; burnt
B．leaving; burning
C．leaving; burnt
D．left; being burnt
地球自转产生了（ ）
①四季更替 ②昼夜更替
③时区差异 ④昼夜长短的变化
A．①②
B．①④
C．②③
D．②④
