Answer: B. trigonal planar
Explanation:
Valence Shell Electron Pair Repulsion Theory (VSEPR) is a model to predict the geometry of the atoms making up a molecule where atoms are arranged such that the forces of repulsion are minimum.
If a central atom is bound to three electron domains ,the number of electron pairs is 3, that means the hybridization will be 
and the electronic geometry of the molecule will be trigonal planar as the electron pairs will repel each other and attain a position which is most stable.
Example: 
with 3 electron domains has trigonal planar geometry.
Put a 2 on the HCl.
2HCl+Ba-->BaCl2+H2
It describes how, when particles/mc/elements react, despite forming different substances the mass is neither created nor destroyed but only converted.
