Dolphins by Wikipedia
Dolphin are aquatic mammals within the infraorder Cetacea. There are 40 species named dolphins. Dolphins range in size from as small as 5 ft 7 in long and 110-pounds to the 31 ft 2 in and 11-short-ton killer whale. Dolphins have streamlined bodies and two limbs that are modified into flippers. Though not quite as flexible as seals, some dolphins can travel at 34.5 mph. Dolphins use their conical shaped teeth to capture fast-moving prey. They have well-developed hearing adapted for both air and water and so well developed that some can survive even if they are blind. They have a layer of fat, or blubber, under the skin to keep warm in the cold water. Although dolphins are widespread, most species prefer the warmer waters of the tropic zones, but some, like the right whale dolphin, prefer colder climates. Dolphins feed largely on fish and squid, but a few, like the killer whale, feed on large mammals, like seals. Dolphins produce a variety of vocalizations, usually in the form of clicks and whistles.
Which sentence best summarizes a central idea of the text?
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5 points
A Dolphins have advanced hearing.
B There is a great variety of dolphins.
C Dolphins mainly live in warm water.
D Dolphins come in many sizes.
Summarize the author’s message about dolphins.