问答题 发育毒性是指出生前经父体或（和）母体接触外源性理化因素，引起在子代到达成体之前这段时间内出现的有害作用。试根据所学知识阐述发育毒性共有哪几个阶段，各阶段有什么特点？

单项选择题 某些物质受到光照射时，除吸收某种波长的光之外，还会发射出比原来吸收波长更长的光。当激发光停止照射时，发光过程几乎立即停止，这种光称为

未知题型 When the key is pressed, the 7-segment digital tube displays ’P’, and the LED is turned on. When the key is released, the 7-segment digital tube displays ’-’, and the LED is turned off. The key is connected to P3.2, as an interrupt 0 input.