You may suppose you have a 0.1 M solution of NH3, from:
NH4Cl + NaOH > NH3 + H2O.
Then you can compute the pH from the concentration of NH3 and its pKb.
The concentration is high enough to use the simplified formula:
[OH] = sqr(Kb*conc)
Why do molecules combined into chains?
B) energy is absorbed by the reaction
is right answer.