技术进步将导致等产量曲线移近原点，不同的技术进步类型还将导致等产量曲线的倾斜度产生不同的变化。
参考答案：对
I prefer () there doing nothing.
A. working than sitting
B. to work than to sit
C. working to sit
D. to work rather than sit
设A是n阶正定矩阵，E是n阶单位阵，证明A+E的行列式大于1．
