pH计的主体是一个（）。
A、精密电位计
B、精密电位计
C、精密电阻计
D、精密pH计
参考答案：B
_____ from his appearance, he is a doctor. [ ]
A. To judge
B. Judged
C. Having been judged
D. Judging
简述转基因动物的应用及意义。
