Questions On Turning Thirty-One, part I by KlionskyG

Question 10

1,1'-(2,2,2-Trichloroethane-1,1-diyl)bis(4-chlorobenzene) has a more common name that has 31 letters (and no numbers). But this molecule is best known by a much shorter name.

Answer either:
- What are the 1st, 9th, and 17th letters of the 31-letter name?
- Alternatively, give the chemical formula of this molecule.

DDT (dichlorodiphenyltrichloroethane) (C14H9Cl5)