The two uses of figurative language that create a vivid understanding of the character Emil are:
b. Emil has been perfecting his robotics project for 50 million years. (This is an exaggeration that emphasizes Emil's dedication and hard work in a humorous way.)
d. Emil is a clever and diligent student who enjoys taking part in the weekly robotics club. (This uses alliteration and descriptiveness to create a clearer and more engaging picture of Emil's character.)
(Note: While option d does not contain traditional figurative language, it uses descriptive language that provides insight into Emil's character.)
To better fit the request for figurative language, option b is clearly the most effective with its hyperbole.