A、Expand operating areas. B、Restrict operating hours. C、Limit the use of water scooters. D、Enforce necessary regulations. D题目问的是

Water scooters are water vehicles that look very much like motorcycles. (21) Nowadays speedy, colorful water scooters are gaining in popularity. They can travel anywhere a small boat can and be typically popular with young people. The rising popularity of the craft has raised the question of water scooter regulation. In this case, the argument for strict regulation is compelling. Water scooters are a particularly deadly form of water recreation. For example, two women were vacationing in Long Boat Key. While they were floating on a rubber boat along the shore, a water scooter crashed into them and killed them. Also, water scooter operators have been killed or seriously injured in collisions with other water craft. Others have been straddled at the sea when the scooters either failed or sank far from shore. (22) Many water scooter operators are inexperienced and ignorant of navigational rules which increases the potential for accidents. The increasing popularity of the scooter has aggravated the problem providing more water vehicles to compete for the same space. Crowded waterways are simply an open invitation to disaster. In addition to the inherent operational hazards of water scooters, they’re proving to be an environmental nonsense. (23) Beach residents complained of the noise of the scooters. The Pacific Whale Foundation on the west coast expressed concern that the scooters are frightening away and endanger species of whale that migrates to Hawaii for breeding. (24) (25) Regulations such as minimum operating age, restricted operating areas and compulsory classes in water safety are essential. Without such regulations, tragedies involving water scooters are sure to multiply which makes many beaches unsafe for recreation.
21．What did the speaker say about water scooters?
22．What does he mentioned as one of the causes of water accidents?
23．In what way is water scooters said to be an environmental nonsense?
24． What does the speaker propose to ensure the safety of beaches for recreation?
25．Which following statement is true?