Answer:
BHx, x=3
CHx, x=4
NHx, x=3
CH2Clx, x=2
Explanation:
We have to know that the value of x must depend on the valency of the central atom. If we look at each of the species;
Boron has a common valency of 3
Carbon has a common valency of 4
Nitrogen has a common valency of 3
The valency of each elements will determine the most likely value of x as outlined in the answer above.