The elements whose oxides can turn phenolphthalein solution pink are:
(a) Na and K
(b) K and C
(c) Na and S
(d) K and P
(a) Na and K
Phenolphthalein works somewhat differently as it is naturally colorless but turns pink in alkaline solutions.
These are basic oxide
Sodium oxide, which reacts with water to produce sodium hydroxide NaOH
Potasium oxide, which reacts with water to produce Potasium hydroxide KOH