Answer:
When respiration occurs without oxygen, lactic acid is produced. Answer is A.
<span>advancing mass of warm air, in particular, the leading edge of the warm sector of a low-pressure system.</span>

<em><u>Nitrogen</u></em><em><u> </u></em><em><u>is</u></em><em><u> </u></em><em><u>not</u></em><em><u> </u></em><em><u>a</u></em><em><u> </u></em><em><u>product</u></em><em><u> </u></em><em><u>of</u></em><em><u> </u></em><em><u>photosynthesis</u></em>