填空:You're dropped ( )"s" in the word "necessary"括号里填 a 还是 an?不是只有元音字母前才加an吗?怎么又有一个"s"了?

问题描述:

填空:You're dropped ( )"s" in the word "necessary"括号里填 a 还是 an?
不是只有元音字母前才加an吗?怎么又有一个"s"了?