Researchers from the united kingdom studied the effect of two breathing frequencies on both performance times and several physiological parameters in front crawl swimming. the breathing frequencies were one breath every second stroke (b2) and one breath every fourth stroke (b4). subjects were 1010 male collegiate swimmers. each subject swam 200 meters,200 meters, once with breathing frequency b2 and once on a different day with breathing frequency b4. describe the design of this matched pairs experiment, including the randomization required by this design.

(a) each swimmer swims one time using each breathing technique (b2 and b4). a coin is tossed to determine the order in which these techniques are used.
(b) each swimmer swims two times using breathing technique b2 or b4. a coin is tossed to determine which technique is used.
(c) each swimmer swims one time using breathing technique b2 or b4.
(d) each swimmer swims two times using each breathing technique (b2 and b4). a coin is tossed to determine the order in which these techniques are used.