The Cos ratio is adjacent/hypotenuse, which in this case uses the 7.8 ft as well as length AC. We can conclude that that will be our ratio.
cos23° = AC/7.8 7.8 (cos23°) = AC
Therefore your answer is D
Side note:
If we were to use angle 67°, we would have to use the Sin ratio (opposite/hypotenuse) to use length AC as well as 7.8 ft. However Sin67° was not an option and so that angle could be ruled out.
