The right answer is D. Cross country runner
The marathoner certainly needs to get muscle but has some condition that should not be very intense.
Cardio and weight training can have a bad influence on each other, but only if they are combined disproportionately, which will prevent you from achieving the goal you set for yourself. A bodybuilder who wants to gain muscle will not achieve visible results if he spends half his training on cardio. In the same way, a marathon runner who wants to improve his performance, will not achieve anything if he focuses on weight lifting.
