下图为DNA分子的某一片段，其中①②③分别表示某种酶的作用部位，则相应的酶依次是

A．DNA连接酶、限制酶、解旋酶

B．限制酶、解旋酶、DNA连接酶

C．限制酶、DNA连接酶、解旋酶解

D．解旋酶、限制酶、DNA连接酶

Being examined twice a year, whether it is a car or a bus or a truck, it is the rule that every driver____ obey in this city.

A．shall

B．can

C．has to

D．need