—Shall I lock the lab before I leave?  

—_____. I'll check it myself later.[ ]

A. Go ahead

B. No problem  

C. No hurry

D. Don't bother

科学家将雌黑鼠乳腺细胞的细胞核移入白鼠去核的卵细胞内，待发育成早期胚胎后移植入褐鼠的子宫，该褐鼠产下小鼠的体色和性别是 [ ]

A．黑、雌

B．褐、雌

C．白、雄

D．黑、雄