What is the best way to rewrite the sentence?
a. before continuing, the climbers will be forced to breathe six to eight times to stop between steps as a result of the high altitude and physical difficulty of the climb.
b. due to the high altitude and physical difficulty of the climb, the climbers will be forced to stop between steps to breathe six to eight times before continuing.
c. the climbers will be forced to stop between steps to breathe six to eight times because of the high altitude and physical difficulty of the climb before continuing.
d. as a result of the high altitude and physical difficulty of the climb, the climbers will be forced to stop between steps before continuing to breathe six to eight times.