1. Some psychiatic studies indicate that among distinguished artists the rates of （manic depression and major-depression are ten to thirteen times as prevalent as in） the population at large.
正确答案: manic depression and major depression are ten to thirteen times more prevalent than in
2. on the Great Plains, nineteenth-century （settlers used mud and grass to build their homes, doing it without timber and nails.）
正确答案: settlers used mud and grass to build their homes, making do without
两个正确答案都搞不懂为什么正确，
第一个为什么去掉 the rates of 呢？
第二个 making do without 是什么意思啊？是怎么一个结构呢？
谢谢
1. Some psychiatic studies indicate that among distinguished artists the rates of （manic depression and major-depression are ten to thirteen times as prevalent as in） the population at large.
正确答案: manic depression and major depression are ten to thirteen times more prevalent than in
同问 比较弱智的问一句 是不是因为major-depression中间的那个横杠根本是不需要的？
2. on the Great Plains, nineteenth-century （settlers used mud and grass to build their homes, doing it without timber and nails.）
正确答案: settlers used mud and grass to build their homes, making do without
()中错在it指代 it试图去指代前面整个事情
make do是固定搭配 见Longman中解释
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make do
to manage with the things that you have, even though this is not really enough
I hardly had any food in the house so I just had to make do.
make do with/without
I usually make do with a cup of coffee for breakfast.
For many people, make do and mend (=when someone manages with the things they have and does not buy anything new) was a harsh reality.