Nhận biết (M1)

Why do rusty-spotted cats purr but jaguars roar? Researchers hypothesize that this difference between the two feline species may be partly due to a U-shaped bone in their throats called the hyoid. Rusty-spotted cats, which are much smaller than jaguars, have a rigid hyoid that rumbles when the cat's larynx vibrates, resulting in a purr. By contrast, jaguars have a somewhat flexible hyoid, and the bone is attached to the skull with a stretchy ligament that rusty-spotted cats lack. These traits allow jaguars and most other species of big cats to produce powerful roars. The same traits may also prevent most big cats from purring.

Which choice best describes the overall structure of the text?

• A.

  The text compares the habitats of two species, then explains how those habitats are changing.

• B.

  The text presents a theory about two species, then discusses facts that weaken it.

• C.

  The text poses a question about two species, then presents a possible answer.

• D.

  The text describes a behavior shared by two species, then discusses other behaviors shared by them.