Answer: Option (b) is the correct answer.
Step-by-step explanation:
A geometry in which the center most atom is bonded to another atoms forming an angle of 180 degrees is called a linear geometry.
For example, in a HCN molecule hydrogen, carbon and nitrogen atoms are attached to each other linearly forming and angle of 180 degrees.
Whereas for a bent geometry will have in total three atoms with one lone pair forming an angle between 90 degree to 120 degrees.
On the other hand, a trigonal pyramidal geometry will have in total four atoms with one lone pair and angle formed will be less than 109 degrees.
Hence, we can conclude that the molecular shape of HCN is linear.