Vinylmethylketone
丁烯酮
??? 情景例句
The little boy held his mother's hand firmly when crossing the street.
那小男孩過馬路時緊抓著母親的手。
By doing we learn.
經一事，長一智。
We also played games on the sand.
我們還在沙灘上做游戲呢。