编写学科课程标准和教材应遵循的原则：思想性和科学性统一；理论联系实际；稳定性和时代性结合：系统性和可接受性结合。(教育学)
参考答案：对
已知圆x2+y2-4ax+2ay+20（a-1）=0．
（1）求证对任意实数a，该圆恒过一定点；
（2）若该圆与圆x2+y2=4相切，求a的值．
Grover Cleveland was the first president () in the White House.
A. got married
B. to get married
C. has got married
D. was married
