字符心理旋转的实验研究表明，当两个被比较对象之间的旋转角度为（）时，其反应时最短。
A.60
B.90
C.180
D.360
参考答案：D
高层民用建筑防烟分区的面积不宜大于()平方米。
A．500
B．1000
C．1500
D．2000
—Welcome to _______ school!
—Thank you. Your school is very modern. [ ]
A. your
B. their
C. his
D. our
