Geneticists studying the gene for lactase did not find any differences in the coding region DNA (the section of DNA with instructions to make the protein) between people who could digest lactose and people who could not digest lactose. After they investigated further, they discovered that the difference between lactose tolerant and intolerant individuals was due to a mutation located in

Explanation:

They discovered that the difference between lactose tolerant/persistence and intolerant individuals was due to a mutation located in another neighbouring gene that controls its persistence.

This gene is the MCM6 gene. This gene affects lactase promoter activity likely causing lactase persistence. It is located in a regulatory region upstream of the lactase (LCT) gene.

c should be the answer