For the following Assertion and Reason, the correct option is 
Assertion (A) : $P{H}_3$ has lower boiling point than $N{H}_3$. 
Reason (R) : In liquid state $N{H}_3$ molecules are associated through vanderwaal’s forces, but $P{H}_3$ molecules are associated through hydrogen bonding. 
In the light of the above statements, choose the correct answer from the option given below.