金融性资产具有流动性、收益性、风险性三种属性，一般认为（）
参考答案：流动性与收益性成反向变化
As the saying goes, one is never too old to learn. After he _____, he will devote himself to gardening.
A．retired
B．has retired
C．will retire
D．had retired
海水结冰与淡水结冰有何不同？为什么？
