同学你好，该知识点来自沪江网校《英语零基础直达大学六级【全额奖学金班】》的课程，想要更系统的学习，欢迎进入课程学习。不仅可以和更多的同学一起学习，而且还有老师、助教随时的学习指导和知识点解答哦。

同学你好~
It is not long before they can pick up weights from the floor of the pool.
floor改成bottom

Now tricycle were lined up on the bottom of the pool.
tricycles 复数
从这句开始时态发生了变化，成了一件过去的事情，所以应该从这句开始另起一段。Now可以去掉。

They soon found their tricycles and started off.
started off their race，加上宾语

A child was first pulling his tricycle, but he found that it was very difficult, then he dropped it.
pulled his tricycle at first，不用进行时，then前加连词and连接句子

祝同学学习进步~