A、underwater explosions B、oil and gas exploration C、whistling of ships D、sonar navigation C

A coalition of environmental groups has urged the United Nations to do more to limit noise pollution deep in the oceans because they said it’s harming whales and dolphins. The Ocean Noise Coalition says the intense sound caused by underwater explosions, oil and gas exploration and sonar navigation needs to be curbed. Martin L has more details.
   "The physical pollution of the oceans has long concerned scientists, but increasingly noise pollution is being regarded as possibly an equal threat to marine life.
   The pitiful sight of great sea mammals like whales and dolphins being washed ashore in large numbers for no obvious reason has got public opinion demanding an answer from the scientists.
   The phenomenon could be caused by cyclical weather patterns. But researchers in several parts of the world are now frequently linking the mass strandings to underwater noise of extremely high volume caused by humans."