Given the task definition and input, reply with output. 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.

Question: If the guanine percentage of a double-stranded DNA molecule is 30%, that of adenine is: 
 Options:  <0> 10% <1> 70% <2> 80% <3> twenty%. <4> 30%

biology