轴承润滑是否正常如何鉴别？

Experiments have proved that children can   1         (instruct) in swimming at a very early age. At a special swimming pool in Los Angeles, children become expert at   2     (hold) their breath under water even before they can walk.          3          (baby) of two months old do not appear to be reluctant to enter the water. It is not long   4        they are so accustomed to swimming   5         they can pick up weights from the floor of the pool. A game that is very popular with these young   6       (swim) is the underwater tricycle race. Tricycles are lined up on the floor of the pool seven feet under water. The children compete against each other to reach the other end of the pool. Many pedal their tricycles,  7      most of them prefer to push or drag them. Some children   8       cover the whole length of the pool   9        coming up for breath even once. Whether they will ever become future Olympic champions, only time will tell. Meanwhile, they should encourage     10         among us who cannot swim five yards before they are gasping for air.