Which of the following is true about past service pension adjustment (PSPA) exempted by CRA? a) A PSPA is exempt from having to be certified if the past service benefit improvement applies to at least 25% of the pension plan members. b) PSPAs that are exempt from certification are included in accumulated PSPA in the current year of the past service event. c) Exempt PSPAs can reduce the RRSP contribution room to a negative amount. d) All of the above is true