A、When they are feeding. B、When it is raining. C、When they are sleeping. D、When they are breathing the air. A短文提到，当鲸群在嬉戏或者在进食的时候

Whale watching is a growing ecotourism industry around the world. It can be emotional, educational and an important part of local economies, offering a unique opportunity for people to appreciate the magnificence of whales in their natural habitat and to help motivate people to protect these animals and their environment. (26) Additionally, much of what scientists know about whales is a result of research conducted while they are aboard commercial whale watching vessels.
     However, unregulated whale watching can also lead to problems, including threats to the animals’ well-being and negative impacts on fragile coastal environments. In addition to increasing  numbers of whale  watching vessels, in many parts of the world,  newer boats are capable of going much faster than in the past, with the increasing likelihood that whales will be hit by boats. The faster a vessel moves, the less likely the operator is to see a distant whale, and the less time they have to react once they do spot an animal. (27)Also researchers have found that if whales are feeding or socializing, they are less likely to react to an oncoming vessel and can be hit.
     In response to this problem, whale watching groups, government agencies and private advocacy groups have established codes of conduct for whale watching.  Under these rules, approaching an area of known whale activity should be done slowly and with caution, stopping to survey the area. (28)In addition, approach parallel to the whales and travel at the same speed as the slowest animals. Stay at least 100 meters away and don’t leapfrog into the path of the whales. Preferably, there should only be two vessels at a time viewing a group of whales.