Detailed Instructions: In this task, you are given a question and answer options for that question. Using this information, you have to classify each text into different topics: medicine, nursery, psychology, chemistry, pharmacology, biology.
Problem:Question: The R-bands of human metaphase chromosomes:
Options: <0> They contain DNA rich in AT pairs. <1> They have high gene density. <2> They contain poor DNA in GC pairs. <3> They replicate at the end of phase S. <4> They have low gene density.
Solution:
biology