基因和尿嘧啶依次存在于（）
A.mRNA和RNA
B.DNA和mRNA
C.转运RNA和DNA
D.DNA和DNA
参考答案：B
Daniel has ________ CDs than Amy, but ________ DVDs than Paul. [ ]
A. more; less
B. more; fewer
C. less; more
D. fewer; less
