In the following passage, some words have been deleted. Read the passage carefully and select the most appropriate option to fill in each blank.

Heat exhaustion can be a recreational hazard, (1) ______ for athletes playing sports outdoors (2) ______ wearing heat-trapping clothing and gear when temperatures are high, (3) ______ as the case in American football. Small studies (4) ______ aimed to design more (5) ______ football uniforms.