Question

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Explanation:

To determine the moon's stage when the lit part is decreasing on the left, we analyze each option:

• Waning: A waning moon has its illuminated portion decreasing. When the left - side lit part decreases, it's a waning phase (e.g., waning gibbous, waning crescent).
• Waxing: A waxing moon has an increasing illuminated portion, so this is incorrect.
• First Quarter: In the first - quarter phase, the moon is waxing (the lit part is increasing), so this is incorrect.

Answer:

A. Waning