What will be the effect of adding 100 mL of 10- 3 M HCl solution to a solution of HA having concentration 0.1 M? (${\mathrm{K}}_{\mathrm{a}}$ of HA = ${10}^{-5}$)

Both degree of dissociation and pH will decrease

Degree of dissociation of HA will decrease, pH will remain constant

Neither pH nor degree of dissociation of HA will change. 

Degree of dissociation of HA will increase and pH decreases.