I am told that the new law will come into ________ on January 1st next year.

A．effect

B．use

C．service

D．existence

鼠的毛色类型由遗传因子B、b控制，甲、乙黑毛雌鼠分别与褐毛雄鼠丙交配，甲3胎共生出9只黑毛幼鼠和7只褐毛幼鼠，乙3胎共生出19只黑毛幼鼠，则甲、乙、丙3只鼠的遗传因子依次可能为（）

A.BB、Bb、bb

B.bb、Bb、BB

C.Bb、BB、bb

D.Bb、bb、BB