共发射极放大电路中三极管的集电极静态电流的大小与（）有关。
A.集电极电阻
B.基极电阻
C.三极管的最大集电极电流
D.负载电阻
参考答案：B
Many students in our school _______ the old and they usually offer their seats to them on buses.
A．worry about
B．care for
C．agree with
D．take care
将重组DNA导入细菌生产激素或蛋白质的过程称为（ ）
A．基因工程
B．细胞工程
C．酶工程
D．蛋白质工程
