1.The missing boy was last seen playing near the East Lake.
1.The missing boy was last seen playing near the East Lake.
2.The little boy was watched to leave the store where he stole several valuable watches.
这两句话对吗?如果将第1句的 playing 改为 to play ;将第2句的 to leave 改为 leaving .为什么?如果对,区别是什么?