Which of the following insects is an efficient pollinator?

Bumble bee is an efficient pollinators.
The bumblebee is a more efficient pollinator at the individual level. It provides highly valued pollination services for a wide variety of crops and ranks as the most frequent single species of pollinator for crops worldwide.
Bumblebees are important pollinators of both crops and wildflowers. Bumblebees are increasingly cultured for agricultural use as pollinators, among other reasons because they can pollinate plants such as tomato in greenhouses by buzz pollination.