Though he was tired, _____ he still studied. [ ]
A. but
B. yet
C. 不填
D. although
答案:C
泛化
决定DNA遗传特异性的是()
A.脱氧核苷酸链上磷酸和脱氧核糖的排列特点
B.嘌吟总数与嘧啶总数的比值
C.碱基互补配对的原则
D.碱基对的排列顺序