Answer;
Light is needed for photosynthesis.
Step-by-step explanation;
Beta Vulgaris also known as beets are cool-weather biennials that are grown as annuals for their leaves and roots. They produce the best quality when grown in cool soil and full sun.
As beets grow and the roots start to bulge out of the soil, it may be advisable to hill soil around them. Keeping the roots covered with soil will protect texture and color.