扫查锁骨下动脉较适宜的探头频率是()
A．2.0MHz
B．2.5MHz
C．5.0MHz
D．10.0MHz
E．12MHz
参考答案：C
用have的适当形式填空。
1. — Do you____an apple? — No, I don't.
2. Linda ____ an English book.
3. They____some books for us.
4. Does Tom _____ a volleyball?
5. We____a soccer ball and a basketball every day.
渠系建筑物中，陡坡、跌水都是落差建筑物。（）
