Answer:
b. Some organisms have a tremendous amount of noncoding DNA, like repetitive sequences.
Explanation:
Eukaryotes looks superficially simple but when we look at the genome of eukaryotes it is seen that it is more complex and much larger than organism who have complex anatomy, structure, and behavior because a large amount of their human genome contains non-coading genes or sequences like introns and repetitive DNA sequence which do not code for any protein.
Therefore the complexity in eukaryotic DNA is because of the noncoding sequence which makes a large amount of eukaryotic genome. So the right answer is b.