花在爱好上英语

Most of the students spend their time on his hobbies, no leisure time to study, they should be reasonable arrangements for holiday time.

I can't decide when to do my homework and when to spend my time on my hobbies.

用 spend 是可以的。下面的阿荣岁月说的不对。Spend time 是经常用到的。没有问题的。

I used to spend a lot of time on his hobbies!

他愿意把时间花在他的爱好上，花时间应该是不用spend，这个单词应该是和花费物品联系，而不是花费时间，你可以问一下你的英语老师。