某一对等位基因（Aa）如果只位于X染色体上，Y上无相应的等位基因，则该性状的遗传不遵循（）定律。
参考答案：孟德尔的分离
Chinese students usually spend _____ the students of the US studying in their free time. [ ]
A. twice as many hours as
B. as twice many hours as
C. twice hours as many as
D. as many as twice hours
关于肝硬化食管静脉破裂出血内科治疗应除外（）
A.普萘洛尔口服或硝酸甘油舌下含服
B.吗啡镇静
C.生长抑素
D.输少白红细胞
E.内镜下静脉套扎
