Which of the following species have the bond angle of $120°$?

According to VSEPR theory, the valance electron of the central atom decides the shape of a molecule. A bond angle is an angle formed between two bonds in a molecule. Either the angle formed between three atoms across at least two bonds or the angle formed between two bonds originating from the same atom often said as the central atom is generally referred to as a bond angle. 

Because every compound has a unique set of atoms and a unique shape, bond angles can be used to discriminate between the geometry of various compounds.
Ammonia has a trigonal pyramidal shape with a bond angle of $107°$.

Bromine trifluoride has a T-shaped structure, with a bond angle of $86°$.

In phosphorous trichloride also, it is a trigonal pyramidal molecule with a bond angle$103°$.

In $B{F}_3$, the molecule has a trigonal planar structure. The bond angle between two B-F bonds is $120°$

Thus, $B{F}_3$ is the right answer.

Hence, the correct answer is option D.