You must spend as much time as you can _________(study)hard

If you're saying how you spent the time (or money), use the -ing form.
If you're saying why you spent the time (or money), use the to --- form.


Last week I spent time cleaning the kitchen floor. 上周我花时间把厨房的地板清洗了.（表示如何把时间花掉的）
Sometimes you have to spend time to make money. 有时候你必须花时间去挣钱.（表示为什么要把时间花掉）


题目： You must spend time(studying / to study) English to catch up with others. 你必须花时间去努力学习英语赶上其他人. （表示的是花时间的目的, 而不是为了超过别人而把时间花掉）
所以正确答案是： 『to study』

You must spend as much time as you can _________(study)hard at English to catch up with others.
这个题是一个典型的【两难选择】，即用两种形式都有道理。也就是说，这是个【失败的题】。
1、You must spend as much time as you can【 studying】ha...

studying,注意句型spendtime (in)doing sth,同时as ... as one can是副词，不是主干，不要被迷惑了

studying因为 spend..... (on) doing