阅读下面材料，在空白处填入适当的内容(1个单词)。
1．He was told that it would be at least three more months________he could recover and return to work.
2．I was watching the news on TV ________ the power went off.
3．This is a very interesting book. I'll buy it, ________ much it may cost.
4. —Look at those clouds!
—Don’t worry. Even________ it rains, we’ll still have a great time.
