下列哪项不是燃气一蒸汽联合循环发电的主要优点（）。
A、电厂的整体循环效率高
B、对环境污染极小
C、调峰性能好、启停快捷
D、燃料便宜
参考答案：D
根据句意和首字母填上适当的单词。
1. My uncle and aunt are ______ (都) workers.
2. We brush (刷) our t______ every day.
3. What's the d______ today? It's October 15.
4. It's not p______ to talk in class.
5. We can get books from the school l______.
6. The fourth day of a week is ______.
在正式场合，西装有三粒扣子，应将（）扣子扣上。
A.上面
B.中间
C.下面
D.无所谓
