AviationTire Principles Of Flight - Aeroplane Subsonic Aerodynamics Means to decrease the CL - CD ratio, increasing drag Q 5 / 5

An aircraft has trailing edge flap positions of 0, 15, 30 and 45 degrees plus slats can be deployed. What will have the greatest negative influence on CL / CD?

Deploying slats.
0 - 15 flaps.
15 - 30 flaps.
30 - 45 flaps.