A mixture of gases at a total pressure of 145.0 kPa contains N2, CO2, and O2. The partial pressure of the N2 is 28.5 kPa and the partial pressure of the CO2 is 76.0 kPa. What is the partial pressure of the O2?
A) 40.5 kPa
B) 41.0 kPa
C) 40.0 kPa
D) 38.5 kPa