In the following question, sentences of a paragraph have been jumbled and labelled as A, B, C, and D. You are required to rearrange the jumbled sentences of the paragraph and mark your response accordingly by selecting the correct option.

A. As genome sequencing has become quicker and cheaper, those studies have become bigger and more complex.
B. As a result, they comb through genomes in search of variations in DNA sequences and use statistical tools to determine whether those variations contribute to traits and diseases.
C. Researchers clearly cannot intentionally introduce mutations into humans; instead, they must use what nature provides.
D. Geneticists have long been able to introduce genetic mutations into model organisms such as the fruit fly — first with X-rays or chemicals, and now with more sophisticated gene-editing tools — where humans are concerned, the toolbox is more limited.