我国的立国之本,中国特色社会主义事业的政治保证是( )
A:坚持以经济建设为中心
B:坚持改革开放
C:坚持科学发展观
D:坚持四项基本原则
In the 1950s in the USA, most families had just one phone at home, and wireless phones _______ yet.
洋务派以“求富”为口号,创办的企业不包括( )