李明和王聪做了如下实验：他们分别把一木块和一铁块同时浸没在水中，松手后发现木块上浮，铁块下沉．对上述现象他俩展开讨论，你认为他们的说法中正确的是（ ）
A．木块受到的浮力比铁块受到的浮力大
B．铁块受到的浮力比木块受到的浮力大
C．木块受到的浮力大于木块的重力，铁块受到的浮力小于铁块的重力
D．密度大的物体下沉，密度小的物体上浮
根据物体的浮沉条件，木块上浮说明木块受的浮力大于木块的重力，铁块下沉说明铁块受的浮力小于铁块的重力，故A、B错，C正确；
密度比液体密度大的物体下沉，比液体密度小的物体上浮（最后漂浮），而密度大的物体却不一定下沉，密度小的物体不一定上浮，故D错．
故选C．
Jogging became popular some twenty years ago and has remained a favorite way of keeping fit．It is running at a steady speed over short or long distances．Teenagers can jog and ，with caution , can people in their seventies . One of the main jogging has over many other sports is that it can be done anywhere . People jog around campuses , in parks and even in urban areas . Special fields and running tracks are not . Similarly , no special is required—no costly hats , gloves , or balls . Good quality running shoes are , but otherwise the jogger can simply wear loose , comfortable clothing . Having bended and as basic warm-up , you are ready to begin jogging now .
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