spend on是指在什么事上花费了时间,后面接的是名词,而spend in doing是指在做什么事上花费了时间,后面接的是动词+ING。
前者是指把某物放在某物上,而后者是花费时间做某事。
spend sometimes to do sth
spend sometimes/somemoney on sth
spend sometimes/somemoney in doing sth
spend time/money on sth
spend time/money in doing sth