In case of emergency, whether knowing how to apply first aid or not really ________ in matters concerning wounds like swollen wrists, broken arms, burns, cuts, and so on.

A．makes difference

B．makes a difference

C．makes differences

D．makes different

封闭型完井方式的井底结构是（）。

A、裸眼

B、固井套管

C、产层上部固井下部裸眼

D、裸眼十砾石充填