Final answer:
When the sun is 20 degrees above the horizon, it is midday. Shadows are at their shortest during this time. Hence the correct answer is option C
Step-by-step explanation:
When the sun is 20 degrees above the horizon, it is midday. At this point, the sun is at its highest point in the sky, known as the zenith, and shadows are at their shortest. After midday, shadows begin to grow longer as the sun descends towards the horizon.
Hence the correct answer is option C