保持什么样的情绪状态，最能提高一个人的学习效率（）
A.稳定的情绪
B.宁静的心境
C.情绪压力
D.适当的焦虑
参考答案：D
Microsoft ended support for Windows XP after April 8, which _______a major operating system for some Chinese computer users, and advised users to upgrade to Windows 8.1.
A．remained
B．remains
C．is remaining
D．is remained
Excel2000具有复杂运算及分析功能。
