问题描述：
upon+doing
"soon you are going to have to move out",cried my neighbor upon seeing the largest tomato plant.
这里的upon seeing怎么解释?
（别用翻译机器翻给我啊,这样我也会的）
"soon you are going to have to move out",cried my neighbor upon seeing the largest tomato plant.
这里的upon seeing怎么解释?
（别用翻译机器翻给我啊,这样我也会的）
问题解答：
我来补答展开全文阅读