In the Section "Investigating Life: Clues to the Origin of Language",what

In the section "Investigating Life: Clues to the Origin of Language",what did scientists discover was the primary cause for language disorder in the affected family?

A) The cause was one mutation in a single gene on one chromosome.
B) The disorder was not inherited but related to diet.
C) Affected family members were lacking vocal chords.
D) The cause was multiple mutations in multiple genes on one chromosome.
E) The cause was multiple mutations in multiple genes on many chromosomes.