Why is pollination done during the day

second sentence of the Explanation.

Explanation:

Pollination is mutually beneficial to plants and to pollinators. Pollination results in the production of seeds and is necessary for many plants to reproduce. Meanwhile, pollinators receive nectar and/or pollen rewards from the flowers that they visit.

Bees have to sleep too. Might as well do it at night, since so few of them are instrument rated for night-time flying.