A mother dolphin(海豚) chats with her baby over the telephone! They were in separate tanks connected by a special underwater audio link. "It seemed clear that they knew who they were talking with", says Don White, whose Project Delphis ran the experiment. But what were they saying Scientists think dolphins "talk" about everything from basic facts like their age to their emotional state. "I speculate that they say things like "there are some good fish over here," or "watch out for that shark because he"s hunting,"" says Denis Herzing, who studies dolphins in the Bahamas. Deciphering(译解) "dolphin speak" is also tricky because their language is so dependent on what they"re doing, whether they"re playing, fighting, or going after tasty fish. During fights, for example, dolphins clap(碰撞) their jaws to say "Back off!" But their jaws clap while playing, too, as if to show who"s king of the underwater playground.

When scientists describe dolphins" communicative skills, their tone is rather ______.

A．affirmative
B．negative
C．playful
D．speculative