自动喷水灭火系统供水设施安装时，当环境温度低于（）℃时，应采取防冻措施。
A、3
B、4
C、5
D、6
参考答案：C
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
番茄为日照中性植物，但要求有充足的光照，一般需（）万Lux的光照强度才能正常生长，其光饱和点是7万Lux。
A.0.5
B.1～2
C.3～4
D.7～8
