Look,that is a boy playing basketball now.
问题描述：
Look,that is a boy playing basketball now.
答
不对,把that 改为 there 就对了.能不能分析下原因There be sb/sth doing sth有某人/某物在干某事。所以得把 that 换为 there我知道there be句型，可是这里动名词短语能不能看成是修饰boy的成分呢可以，但是你前面有Look在，不合适。