引种驯化试验包括()
A. 种源试验
B. 品种比较试验
C. 区域试验
D. 繁殖推广
Chinese language is written in the form of__, so people also call Chinese characters “Fang Kuai Zi” in Chinese()
A. square
B. circle
C. rectangle
D. triangle
当NPN型三极管的VCE > VBE且VBE >0.5V时,则三极管工作在()
A. 截止区
B. 放大区
C. 饱和区
D. 击穿区
下列三极管各个极的电位,处于放大状态的三极管是()
A. VC=0.3V,VE=0V, VB=0.7
B. VC=-4V, VE=-7.4V,VB=-6.7V
C. VC=6V, VE=0V, VB=-3V
D. VC=2V, VE=2V, VB=2.7V