改错：She studied her hands for a moment and looked down.为什么把do

在某种意义上,你可以把 upon 看作 on,英语中这些小词一般都没什么特定的意思的.例如：agree upon sb.= agree on sb.
不过这句话应该改成 up 吧.
很明显,意思是说,她低着头看了看自己的手后抬起头了.
she studied her hands for a moment and looked up.
P.S.:look on = look upon 意为：认为,看待,以某种方式看待
例：The manager looked upon/on them as incompetents
经理认为他们不够胜任
改错不一定都在改语言,也要注意语境的.
希望帮到你了哈!