Complete the sentences with the given words in their proper forms（用括号中所给单词的适当形式完成下列句子）：

【1】Peter wanted to be a volunteer at the library on his _______ birthday. （twelve）

【2】English is one of the official _______ in India. （language）

【3】Step back and you will find a good way to _______ the problem. （solution）

【4】You can find some _______ books in our school library. （amaze）

【5】The scientist had many _______ in his life. （invent）

【6】We all know computers are _______ machines. （power）