Final answer:
The crab will take 4/5 of an hour (48 minutes) to reach the beach.
Step-by-step explanation:
To calculate the time it will take for the crab to reach the beach, we can use the formula: time = distance / speed. In this case, the distance is one-fifth of a mile and the speed is 1/4 of a mile an hour. So, the time it will take for the crab to reach the beach is:
time = (1/5) / (1/4) = (1/5) * (4/1) = 4/5
Therefore, it will take the crab 4/5 of an hour to reach the beach, which is equivalent to 48 minutes. So, the answer to the question is not listed, but it would be 48 minutes.