On 23rd December, 2013, Michael Schumacher -- the famous Formula-One race car driver -- received serious brain injuries after hitting his head on a rock while downhill skiing with his son. The accident happened during a family holiday in the French Alps. Although he was wearing a helmet, which broke apart on impact, the F1 celebrity was moving at speeds of up to 62 mph and skiing outside the off-piste safety demarcations  . Doctors reported that he would have died on impact if he hadn't been wearing a helmet. He has been in a coma   since arriving at a nearby hospital where he was airlifted to from the site of the accident. Michael Schumacher grew up in frugal   conditions and started what would become his remarkable professional career when his working class father -- a bricklayer -- built him a _ from where he started participating in competitions. He started his adult career racing for Formula Ford in 1988 and later raced for Formula One Ford, Ferrari, and Mercedes AMG. He holds numerous F1 world records including most race victories, fastest laps, and most races won in a single season. According to the Formula One website, he is "statistically the greatest driver the sport has ever seen". Also notable are his contributions to charity, during the peak of his career he has given away more than 50 million Euros to a variety of charity organizations, most to help children around the world. Millions of Europeans and other fans around the world are holding their breath and waiting for information about his hopeful recovery. We wish him and his family the best. What is a  _  most likely to be?
A medical instrument. A small car-racing field. A racing-car driver's safety helmet. A small motor vehicle used for racing.