One difference between dna and rna is that
a) adenine is found only in rna.
b) guanine is found only in dna.
c) cytosine is found only in rna.
d) thymine is found only in dna.

D. Thymine is found only in DNA

Explanation:

DNA is a long polymer with deoxyriboses and phosphate backbone. Having four different nitrogenous bases: adenine, guanine, cytosine and thymine.

RNA is a polymer with a ribose and phosphate backbone. Four different nitrogenous bases: adenine, guanine, cytosine, and uracil.

you are certainly talking about this picture:

a: is the label of the white square, it is showing the  replication fork, formed by helicase (d) ==> so it is the site of dna separation and replication 

b: is a new dna brand that is following directly the replication fork, so it is continuous ==> built continuously from 5' to 3

c: dna polymerase cannot replicate dna on its own, it needs the of their proteins, and one of them plays the role of a clamp which fixes  the dna with the dna template and increases  the processivity of the enzyme. ==>   stops polymerase from falling off the  template.

d: is the enzyme responsible for forming the replication fork (helicase) ==> unwinds and separates dna into two strands

e: is the delayed strand, it is built  in the opposite sense of the helicase, so dna will be built in fragments ==> built  fragments from 5' to 3 joins

and finally f: is the enzyme that builds  the new dna strand (dna polymerase) ==>   adds nucleotides to make a new dna helix.

credit: gradman555p98x9p

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