What will be the likely outside temperature?

The answer is B. -4.6F. 

Reasoning/math:
The given is that ground temp. (which is 0 altitude) is 5. One increment up from that would be 500 altitude = 3.4 temp. Continuing from there, it's 1000 altitude = 1.8 temp, 1500 altitude = 0.2 temp, 2000 altitude = -1.4 temp, 2500 altitude = -3 temp, and finally 3000 altitude = -4.6 temp.

-9. 6
If every 500 it drops 1.6 you do 1.6 times 6 (3000/500=6). You get 9.6 but since it's dropping you put a negative sign.