作为物质交换的场所，毛细血管不具有的特点是： A．分布极广 B．管壁极薄 C．管

表皮黑素单元（epidermalmelaninunit）

设齐次线性方程组

的系数矩阵A=(a_ij)_n×n的秩为n-1，试证：此方程组的一般解(全部解)为

其中A_ij(1≤j≤n)是a_ij的代数余子式，且至少有一个A_ij≠0．

什么是信用创造？

普通抹灰，立面要垂直，质量允许偏差______。

A．2mm

B．3mm

C．4mm

D．5mm

The winner of the Nobel Prize in physics dedicated the honor to his high school physics teacher, he had been an inspiration during his early years.

A. who



B. whom
C. which


D. that