In general,the amount that a student spends on housing should be held to one-fifth of the total___for living expenses.
问题描述：
In general,the amount that a student spends on housing should be held to one-fifth of the total___for living expenses.
acceptable\available为什么选available?
答
句子可以理解为
In general, the amount that a student spends on housing should be held to one-fifth of the total (amount that is) available for (allocating to) living expenses.
在这个语境里 available for 有 “可用于” ,“可供分配给” 的意思 ,
one-fifth of the total (amount that is) available for (allocating to) living expenses
= 可供分配给生活费用的总额的20% .