Final answer:
In 'A Cub Pilot,' a steamboat pilot needs a keen memory due to the continuously changing physical features of the river. The passage illustrating changing street signs best supports the importance of memory for river navigation.
Step-by-step explanation:
In “A Cub Pilot,” the narrator believes that it is so important for a steamboat pilot to have a good memory because the river’s physical features are constantly changing and are hard to keep straight. Pilots must remember every minor detail of the extensive river to navigate successfully, making a keen memory crucial for their job performance and safety. The best statement from “A Cub Pilot” that supports this answer is, “If you will take half of the signs in that long street, and change their places once a month, and still manage to know their new positions . . . you will understand what is required of a pilot’s peerless memory.” This comparison illustrates the need for a pilot to adapt to an ever-changing environment, which relies heavily on the strength of their memory.