如图所示的电路中，电源两端电压不变，电流表和电压表选择的量程分别为0～0.6A和0～3V。闭合开关S，在滑动变阻器滑片P从一端移动到另一端的过程中，电压表和电流表的示数均可达到各自的最大测量值(且不超过量程)，在上述过程中，电阻R₁消耗的最大电功率与最小电功率之比为9:1。则当滑片P移至滑动变阻器的中点时(   )

    Do you know that fish come out of eggs when they were born? After the baby fish comes out of the egg，it eats the food in the egg. When it is big enough，it leaves the egg. It swims in the water. You can see the eyes and the nose. Its ears are hidden (藏) in the head.

    Some fish eat other fish. The fish that eat plants have smaller mouths and teeth. The fish that eat other fish need larger mouths and stronger teeth.

Fish are usually dark on the top and light on the bottom.