Observations of cetaceans in the wild have provided some insights on their learning abilit

ies. Several bottlenose dolphins off western Australia, for instance, have been observed carrying large cone-shaped sponges over their beaks. They supposedly use the sponges for protection against stingrays and other hazards on the bottom as they search for fish to eat. This is the first record of the use of tools among wild cetaceans.

What does the author conclude about the intelligence of cetaceans？

A．It is not appropriate to judge cetacean intelligence in human terms.

B．Cetaceans probably possess a mental sophistication that is as complex as that of humans.

C．Although cetaceans may appear to be intelligent, they have fewer problem-solving skills than most animals,

D．Their ability to learn American Sign Language indicates that cetaceans have a high level of intelligence.