Given
The situation would best be represented by positive 6
Solution
Let us look at the first option
A. Taking an elevator down 6 floors in a building
Since it is coming down, this situation represents negative 6
B. Deleting 6 photos from a camera's memory card
Since we are removing, it also represent negative 6
C. A plant growing 6 inches
This is increasing and gaining height, so it represent positive 6
D. A group of 6 students getting off a bus
This also is a situation of negative 6, since the students are coming off the vehicle.
Therefore the right option is C
Option C