A DNA nucleotide may consist of（）
A. a
B. ribose sugar, a phosphate group, and adenine
C. B．a phosphate group, deoxyribose, and cytosine
D. C．uracil
E. deoxyribose, and a phosphate group
F. D．deoxyribose
G. thymine, and a hydroxyl group
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A nucleoside consists of a（）
A. pentose
B. sugar and a nitrogenous base
C. B．phosphate
D. group and a nitrogenous base
E. C．pentose
F. sugar and a phosphate group
G. D．pentose
H. sugar, a phosphate group, and a nitrogenous base
The following preparations should be made before meeting visitors（）
A. necessary items
B. image preparation
C. knowledge preparation
D. itinerary preparation
The Tujia people called themselves “Bizika” , which means “_“（）
A. foreign dwellers
B. native dwellers
C. Tujia people
D. overseas people
Data collected over several time periods are（）
A. time series data
B. time controlled data
C. crossectional data
D. time crossectional data
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