操纵子学说是原核生物基因调控的重要方式。主要为负调控方式的是
A．乳糖操纵子
B．色氨酸操纵子
C．阿拉伯操纵子
D．葡萄糖操纵子
参考答案：A,B
You must remember that you ______ feed the fish much. [ ]
A. don't need to
B. needn't to
C. don't need
D. not need
