In most birds air sacs are ____________ in number?
Correct answer: D. 9
- A. 10
- B. 3
- C. 4
- D. 9
Explanation
Most birds have nine air sacs: cervical, clavicular, anterior thoracic, posterior thoracic and abdominal sacs. These sacs act as bellows and maintain a continuous flow of air through the lungs. The common mistake is choosing 10 by confusing the number of air sacs with the number of lungs or air passages.
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