心房颤动最常见于
A．冠心病B．风心病二尖瓣狭窄C．高心病D．甲亢性心脏病E．缩窄性心包炎
参考答案：B
抛物线 y=-x2+1 的开口向（ ）。
用所给单词的适当形式填空.
1. It's winter in France. The weather is (wind).
2. They (clean) the classroom now.
3. We are (surprise) to hear the bad news.
4. Some (scarf) are on the box.
5. The (man) are our teachers.
