Locate the sentences below in the article "Dolphin Communication." Which of them is used as a transition?
A
Whistling also helps these marine mammals coordinate their pursuit of food. (paragraph 6)

B
Should the mother and calf become separated, they each whistle until they find each other again. (paragraph 5)

C
They can also mimic many different sounds, from the sounds of other dolphins to sounds made by boats and human beings. (paragraph 4)

D
Scientists believe this is because of the speed with which sound travels through water, making it a more efficient form of communication than other methods. (paragraph 3)