优化公共资源配置的重点是（）。
A.发展社会事业
B.解决民生问题
C.发展民主政治
D.维护国家安全
参考答案：A, B
We are taught that a business letter should be written in a formal style ________ in a personal style.[ ]
A. rather than
B. other than
C. better than
D. more than
简述晶体的球面投影。
