Which of the modern technology has helped professional swimmers improve their racing performance?
A) flippers for protection
B)swimsuits for permitting drag
C) earpieces for listening to coaches
D)mouthpieces for breathing
I am pretty confident that the answer is D) mouthpieces for breathing. This is the only way they can stay underwater for long periods of time. If they came up every 10 seconds for breath, they would waste a lot of time.
