甲、乙两种物质的质量和体积关系图象如图所示，分别用甲、乙两种物质制成体积相等的A、B两个实心物体，浸没在水中放手，待物体稳定后（　　）

A

    Skin­diving is a new sport today. This sport takes you into a wonderful new world. It is like a visit to the moon. When you are under the water, it is easy for you to climb big rocks, because you are no longer heavy.

    Here, under the water, everything is blue and green. During the day, there is plenty of light. When fish swim nearby, you can catch them with your hands.

When you have tanks of oxygen on your back, you can stay in deep water for a long time. But you must be careful when you dive in deep water.

    To catch fish is one of the most interesting parts of this sport.

    What's more, there are more uses for skin­diving. You can clean ships without taking them out of water. You can get many things from the deep sea.

    Now you see that skin­diving is both useful and interesting.