A primary standard solution is a highly purified compound that is used to standardise a solution of known concentration for use in titrations and other analytical chemistry procedures.
Potassium hydrogen phthalate is primary standard for NaOH. Formula for Potassium hydrogen phthalate is C6H5O4K. It behaves as a monobasic acid.
Phenolphthalein is used as an indicator in this titration.
The reaction is,

Hence option A is the answer.