In a given population of plants there is variation in the time of day when flowers open. Those individual plants with flowers that open at night would be more likely to pass on this trait in an environment dominated by what?

The question is incomplete as it does not have the options which are:

Solar radiation

Nocturnal pollinators

Moist soil

Grazing animals

Nocturnal pollinators

Explanation:

Flowers are the reproductive organ of the flower which encloses the reproductive organs in very colourful petals which produce fragrance.

The colour of the petals, the fragrance, the nectar production and the opening of the flower are the result of the evolutionary adaptations under the force of natural selection (pollinators).

The flowers which open at night time are found in the areas where the nocturnal species are found in the highest number. The flower in this area opens at night with fragrance and the white petals so that they can attract the nocturnal pollinators.

Thus, Nocturnal pollinators are correct.