Choose the suitable word to fill in each plank.

Every year since 1986, some of the world's most daring runners have (21)__________ in the desert of Morocco. They are there to take (22) _____ in one of the most difficult races in the world. The Marathon of the Sands, as it is called, covers over 125 miles of desert and mountain wilderness. The runners (23) _______ the course in fewer than seven days, and they run with their food, clothing, and sleeping bags on their backs. The Marathon of the Sands was founded in 1986 by Patrick Bauer.

His idea was to give the runners, (24) ________ come from all over the world, a special kind of adventure. Most of the runners in this race have found that they form deep friendships with the other runners during their days and nights in the desert. Facing terrible (25) ______ and complete exhaustion, they learn much about themselves and other people.

Every year since 1986, some of the world's most daring runners have (21)__________ in the desert of Morocco.