what os the best estimate

Answer:
B
Step-by-step explanation:
To start, the length of a bathtub is not less than a foot, or anything near that, so we can rule out A and C. Next, bathtubs can come in various sizes, but they are all near 5 feet, and 15 feet is very long. It is longer than the tallest person on Earth, so that is not an option, so the answer is B.