Answer: Choice D
Step-by-step explanation:
The red arrow indicates moving 2 units to the left from 0 as the start point. So the red arrow represents -2.
The blue arrow represents moving 4 more units to the left, so it indicates -4.
Put together, -2-4 = -6 means we first move 2 units to the left, then another 4 units to the left, to arrive at -6 on the number line. This is of course when we start at 0.