.-----I heard that many westerners prefer vegetables to meat.

-----It is true. Americans eat ___ vegetables each person today as they did 20 years ago.

A．more than twice

B．as twice as many

C．twice as many

D．that twice as many

1996年在英国出生的克隆绵羊“多利”，是将白面绵羊的乳腺细胞核移植到黑面绵羊的去核卵细胞中．形成重组细胞后经一系列培育而成．根据遗传学原理，分析“多利”的面部毛色应是（　　）

A．黑色

B．黑白相间

C．白色

D．不确定