Answer : 2. "3' > 2' > 1'> NH3"
Explanation :

Answer: B) 3' > 2' > 1'> NH3 Explanation: The order of basicity in ammonia is different in gaseous phases vs. aqueous phases due to hydrogen bonding.   So in gaseous phases it's the well known: 3' > 2' > 1'> NH3. Just so we're on the same page, this is due to the inductive effect of electron donating alkyl groups--they destabilize the lone pair on nitrogen atom, making nitrogen more basic.   But in aqueous phase, the order is slightly different: 2'> 1'> 3' > NH3.