元朝时，黄道婆推广了_________________先进的棉纺织技术。 [ ]
A．回族
B．彝族
C．藏族
D．黎族
答案：D
—Could you tell ______it is from your home to your school?
—It’s about fifteen minutes’ ride.
A．how long
B．how often
C．how far
D．how soon
下列离子中，所带电荷数与该离子的核外电子层数相等的是 [ ]
A．Al3+
B．Mg2+
C．Be2+
D．H+
