如图所示，用铆钉连接上下两块钢板，钢板厚度均为t，铆钉直径为d，铆钉的挤压应力σbs

已知函数f（x）=log_a（1-x）+log_a（x+3）（a＞0，a≠1）．

（1）求函数f（x）的定义域；

（2）当0＜a＜1时，求函数f（x）的最小值．

遗传性球形红细胞增多症的发病机制?

—What’s your plan for the summer holidays?

—I’ll go to Beijing       the school terms ends.

A．in order that

B．so that

C．as soon as

D．even though

It's ____ for children to watch little ants carry food home busily. [ ]

A. interested

B. interesting

C. interest

D. interests