下列关于芽孢的叙述错误的是( )
A.芽孢是细菌在不良环境中形成的结构
B.芽孢是细菌的休眠体
C.芽孢可以萌发出一个细菌
D.芽孢和孢子一样是细菌用来繁殖的结构
答案:D
PIN器件本身噪声的主要来源()。
A.背景电流
B.热噪声
C.暗电流
D.过剩噪声
I was late for school today because my alarm clock _ . [ ]
A. went off
B. had gone off
C. stopped
D. had stopped