1. The text is divided into sections with subheadings. In the section called "Inherited Disorder," what does the author describe
A. the mutation that causes the C-A-G section of the huntingtin gene to repeat more than 17 or 18 times
B. the huntingtin protein and the work that Carroll and his colleagues at UBC are conducting on mice
C. the loss of nerve cells in the region of the brain that controls movement and possibly cognition
D. the characteristics of Huntington's disease and Carroll's family history with the disease