— No, you don't have to, but you give them to me tomorrow.
A:May, can
B:Should, must
C:Can, can
D:Must, had better
不可以构成一个生态系统的是( )
调查动物种群密度的正确方法是:
小军手里有一个额定电压为6V,正常工作电流约为0.5A的小灯泡,他想利用小灯泡探究“电流和电压的关系”,电源电压为9V.