Read the passage carefully and choose the correct answer

Completing a marathon is considered very difficult, but many coaches believe that it is possible for anyone who is willing to put in the time and effort. Obviously, most participants do not run a marathon to win. More important for most runners is their personal finish time and their placement within their specific age group and gender. Another very important goal is to break certain time barriers. For example, ambitious recreational first-timers often try to run the marathon under 4 hours; more competitive runners will attempt to run under 3 hours. Many runners then prefer to finish for example in 3:29:59, which makes them “sub-3:30h marathoners”, instead of 3:30:01.

For most runners, the marathon is the longest run they have ever attempted. Many coaches believe that the most important element in marathon training is the long run. Recreational runners commonly try to reach a maximum of about 20 Emiles in their longest weekly run and about 40 miles a week in total when training for the marathon. More experienced marathoners may run a longer distance. During marathon training, adequate recovery time is crucial. If fatigue or pain is felt, it is recommended to take a break for a couple of days or more to let the body heal. Overtraining is a condition that results from not getting enough rest to allow the body to recover from difficult training. It can actually result in a lower endurance and speed and place a runner at a greater risk of injury.

A marathon completion is ____.

• A. 
  impossible
• B. 
  easy
• C. 
  not very difficult
• D. 
  very difficult