阅读理解。 Water skiing is a sport with many social, economic and health benefits to society. It is unique in that it is a sport where able and disabled persons, and people as young as 5 years and as old as 80 years of age can participate alongside each other. It is a sport that involves more than one person, and is a wonderful family activity that gathers members together for a day of fun at a favorite waterway. Anyone who has put on water skis can attest to its health benefits-it is a sport that demands and develops strength, agility and endurance. The sport includes several disciplines(训练) including slalom, tricks, cable, jump, ski racing, kneeboard, wakeboard, and barefoot, with each of these practiced for either recreational or competitive enjoyment. Safety Tips for Water-Skiers Don't take unnecessary risks while water-skiing. The following tips will help you safely enjoy this thrilling sport: ALWAYS have an observer in the boat. This is a legal requirement in many states. The boat driver cannot watch the skier and operate the boat safely at the same time. ALWAYS wear a Coast Guard approved Personal Flotation Device (PFD) designed for water skiing.  Ski belts are NOT recommended. Your approved PFD will help keep you afloat. NEVER ski in rough water. High waves or a choppy sea will prevent the tow boat from maintaining a steady course and speed. NEVER ski after dark. It is dangerous AND illegal. Any boat traveling fast enough to tow a skier is traveling too fast to navigate safely at night. NEVER water-ski while under the influence of alcohol or drugs. Such activity is extremely dangerous because of the impairment to your judgment and ability to respond. A recent study conducted with expert skiers who were purposely drunk indicated that even their ability to ski was dramatically reduced. Use hand signals between the skier and observer. Agree before you start what each signal means so there is no confusion at a critical moment. 1. Who can accompany you to go water skiing? A. A pupil in a primary school. B. A person who is disabled. C. A family member. D. All above. 2. Which is WRONG according to the passage? A. Water skiing helps build up one's strength. B. The disciplines mentioned are only for competitions. C. Hand signals should be agreed on before skiing. D. Rough water makes the tow boat less steady 3. Which of the following is against law while water skiing? A. An observer doesn't watch the skier. B. A skier doesn't fasten his safe belt. C. Go skiing at midnight. D. Go skiing after drinking wine. 4. The purpose of the article is to . A. warn people of the danger of skiing B. tell how to enjoy water skiing properly and safely C. tell people, both young and old, to learn to ski D. tell people not to go skiing after drinking too much