spend的基本句式：
spend…on sth
spend…in doing sth
老师说有时用: spend…on doing sth
请问：spend…in doing sth与spend…on doing sth有什么不同？
▲spendin doing sth与spendon doing sth都可以表示花费资金做某事，一般可以互换用。比如：
He spends a lot of money on entertaining friends.
He spends his whole life in looking after the poor.
▲表示花浪费时间间做某事时，spendin doing sth 和 spendon sth 在语义上有所不同。比如：
He spent half a year on writing a short play. 他把半年工夫花费在写 一个短剧上。
He spent half a year in writing a short play. 他费了半年写 一个短剧。
摘自《薄冰英语惯使用方法词典》p.1006
