元朝时,在我国形成的一个新民族是 [ ]
A、藏族
B、蒙古族
C、回族
D、满族
答案:C
--I once got lost during my first visit to Beijing.
-- Oh, did you? You ____ me as your guide.
A.might have asked
B.could ask
C.would have asked
D.would ask
下列有关PrP的描述,错误的是:()
A.可致海绵状脑病
B.有两种异构体
C.含有核酸
D.需要特殊消毒才能灭活