海豚被认为是地球上最聪明的动物之一。
Dolphins are often regarded as one of Earth's most intelligent animals. They are social creatures, living in pods of up to a dozen individuals. In places with a high abundance of food, pods can merge temporarily, forming a superpod; such groupings may exceed 1,000 dolphins. They communicate using a variety of clicks, whistle-like sounds and other vocalizations.

Membership in pods is not rigid; interchange is common. Dolphins can, however, establish strong social bonds; they will stay with injured or ill individuals, even helping them to breathe by bringing them to the surface if needed. This altruism does not appear to be limited to their own species. The dolphin Moko in New Zealand has been observed guiding a female Pygmy Sperm Whale together with her calf out of shallow water where they had stranded several times. They have also been seen protecting swimmers from sharks by swimming circles around the swimmers or charging the sharks to make them go away.

Dolphins also display culture, something long believed to be unique to humans. In May 2005, a discovery in Australia found Indo-Pacific bottlenose dolphins (Tursiops aduncus) teaching their young to use tools. They cover their snouts with sponges to protect them while foraging (looking or searching for food or provisions.) Using sponges as mouth protection as well as other transmitted behavior proves dolphins' intelligence. This knowledge is mostly transferred by mothers to daughters.

根据上文判断对错

Dolphins are solitary creatures. 

a.  True

b.  False 

Dolphins are altruistic. 

a.  True.

b.  False.

Dolphins teach each other some behaviors.

a.  True

b.  False