Pipe A fills the tank in 6 hours, Pipe B fills it in 8 hours, and Pipe C empties it in 12 hours. With all three open together, we need the time to fill the tank. We can check each option by seeing whether the combined work done over that time adds up to exactly 1 full tank.
Only 4 hours 48 minutes gives a combined fraction filled of exactly 1, meaning the tank is exactly full at that point.
Therefore, the correct answer is 4 hours 48 minutes.
Let the tank's capacity be 24 units, chosen as the least common multiple of 6, 8 and 12 so that every pipe's rate comes out as a whole number. Pipe A then fills \( \frac{24}{6}=4 \) units per hour, Pipe B fills \( \frac{24}{8}=3 \) units per hour, and Pipe C drains \( \frac{24}{12}=2 \) units per hour. With all three running together, the net rate is \( 4+3-2=5 \) units per hour, so the tank of 24 units fills in \( \frac{24}{5}=4.8 \) hours, which is 4 hours and 48 minutes. Check this net rate against each option.
Working in whole-number capacity units shows the net fill rate is 5 units per hour, and the 24-unit tank fills exactly at 4 hours 48 minutes.
Therefore, the correct answer is 4 hours 48 minutes.