Passage:

In angiosperms both male and female gametes are non-motile, therefore, to bring them together for fertilisation to occur, angiosperms developed special mechanism can called pollination. Transfer of pollen grains  from the anther to the stigma of a pistil is termed pollination. Depending on the source of pollen, pollination can be divided into three types- autogamy, geitonogamy and xenogamy. Plants use two abiotic (wind and water) and one biotic (animals) agents to achieve pollination. Pollination by wind is more common amongst abiotic pollinations. Wind pollination also requires that the pollen grains are light and non-sticky so that they can be transported in wind currents. They often possess well-exposed and large often-feathery stigma to easily trap air-borne pollen grains. Wind pollinated flowers often have a single ovule in each ovary and numerous flowers packed into an inflorescence. Pollination by water is quite rare in flowering plants and is limited to about 30 genera, mostly monocotyledons. Some examples of water pollinated plants are Vallisneria and Hydrilla which grow in fresh water and several marine sea-grasses such as Zostera. Not all aquatic plants use water for pollination. In a majority of aquatic plants such as water hyacinth and water lily, the flowers emerge above the level of water and are pollinated by insects or wind as in most of the land plants. 
Majority of flowering plants use a range of animals as pollinating agents. Among the animals, insects, particularly bees are the dominant biotic pollinating agents. To sustain animal visits, the flowers have to provide rewards to the animals.

Question:

The most dominating biotic pollinating agent is