The correct answer is option-1, swimming. Athletes with a higher proportion of red fibers in their muscles are better equipped for swimming. Red fibers, also known as slow-twitch fibers, have high endurance and are more resistant to fatigue. They generate energy aerobically, meaning they use oxygen to produce energy. This is beneficial for activities that require sustained effort, such as swimming.

Option-2, sprinting, would require fast-twitch muscle fibers for explosive bursts of speed, rather than the endurance provided by red fibers. Option-3, short activities, is vague and could potentially refer to a variety of activities. Option-4, shot put, is a power-based activity that would rely more on fast-twitch fibers for explosive strength.

In summary, red fibers are best suited for endurance-based activities like swimming, making option-1 the correct answer.