Suppose the CPI last year is 121 and the CPI this year is 137. The correct method to calculate the inflation rate is:

A. (137 - 121)/100 = 0.16

B. 137 × 121 = 258

C. [(137 – 121)/121] × 100 = 13.2

D. (137/121) × 100 = 113.2