This was not a popular question among the candidates and performance was below average.      Majority of the candidates that attempted this question were ignorant of the concept of interpretation of planck’s theory graphically.  Teachers are encouraged to feature deductions from graph prominently in candidates class work.
          The expected answers are:
         (a)    slope represents the Plank’s constant.
         (b)    intercept OC represents the  work function (of the metal)
         (c)    intercept OK represents the threshold frequency fo of the incident radiation