The answer is D. multiple alleles
Answer:D
Explanation: The pulmonary air sacs of birds only permit a unidirectional flow of air through the lungs. Unidirectional flow means that air is inhale and exhale through one trachea alternatively. This means the bird lungs only receive largely fresh air which has a high oxygen content during inhalation and do not receive fresh during exhalation. While air flow bidirectional in mammals.
The best and most correct answer among the choices provided by your question is the first choice or letter A. <span>A biological agent that cannot reproduce on its own is a VIRUS.
</span>A virus<span> is a small infectious agent that replicates only inside the living cells of other organisms.
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Wingspaninson famous for ther poetic forms, verse, and sonnet
So, the correct answer would be : A. Brooks Wingspaninson
while Brooks often wrote lyric poetry, winspaninson experimented with a range of poetic forms, including narrative, free verse, and sonnet
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