我知道用英语怎么说

1、我知道用英语说法是：I Know。

2、例句：I know peoples handwriting changes as they get older. 意思是：我知道人们的笔迹随着年龄的增长而变化。He went very quiet so I knew he was upset.意思是：他沉默不语了，所以我知道他很烦恼。