helplessly
adverb /ˈhelpləsli/
  /ˈhelpləsli/
- in a way that shows that you are unable to do anything in a particular situation 
无助: 以某种方式表明您无法在特定情况下执行任何操作- They watched helplessly as their home went up in flames.
他们无奈地看着自己的家被大火吞没。  
 - They watched helplessly as their home went up in flames.
 - in a way that shows that you are unable to control a strong feeling
无法抑制的 - Both sisters started to laugh helplessly.
姐妹俩开始无奈的笑了起来。  
 - Both sisters started to laugh helplessly.