哪一项不是幸福的原则？（）
A、选择原则
B、行动原则
C、认识原则
D、努力原则
参考答案：D
抛物线y2=x的准线方程为______．
I’m pleased ______ should be done has already been done.
A．with what
B．that that
C．by that
D．that what
