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多项选择题

含两个自变量的二阶线性偏微分方程的分类是（）。

A．抛物型方程
B．线性方程
C．椭圆型方程
D．双曲型方程

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热门试题

单项选择题According to the research, women who could outearn their husbands choose not to work at all, or to work less because _____.

A．they need to take care of the children and household chores
B．they think husbands should give more financial support to the family.
C．they still need to take more responsibilities at home to soothe their husbands’ unease at earning less
D．they don’t like competition in companies

单项选择题任何一个有彩色加( )色,它的纯度会骤降。A. 白色B. 黑色C. 灰色D. 补色