Question

the trachea, or windpipe, branches into...
the alveoli, two smaller air sacs within the lungs.
the bronchi, two smaller air sacs within the lungs.
the bronchi, two smaller tubes that move toward the lungs.
the alveoli, two smaller tubes that move toward the lungs.

Explanation:

To solve this, we recall the respiratory system anatomy: The trachea (windpipe) branches into the bronchi (two tubes that lead toward the lungs). Alveoli are tiny air sacs at the end of bronchioles, not a direct branch of the trachea. Also, bronchi are tubes (not air sacs) and alveoli are sacs (not tubes). So we analyze each option:

• First option: Alveoli are not a direct branch of trachea, and they are air sacs but not a branch here. Eliminate.
• Second option: Bronchi are tubes, not air sacs. Eliminate.
• Third option: Trachea branches into bronchi (two tubes moving toward lungs). Correct description.
• Fourth option: Alveoli are not tubes and not a direct branch of trachea. Eliminate.

Answer:

C. the bronchi, two smaller tubes that move toward the lungs. (Note: Assuming the third option is labeled C; if the original options have different labels, adjust accordingly. Based on the text, the third option is "the bronchi, two smaller tubes that move toward the lungs.")