根据下表内容判断,下列说法正确的是
A.①③
B.②③
C.①④
D.②④
答案:C
It is necessary for us _______them every day.
A.looking after
B.to look after
C.look after
D.to looking after
PT泵在结构上是以燃油泵()和喷油器进油时间对进油量的影响来控制供油量。