A mixture of gases at a total pressure of 95 kPa contains nitrogen, carbon dioxide and oxygen. The partial pressure of carbon dioxde is 24 kPa and the partial pressure of the nitrogen is 48 kPa. What is the partial pressure of the oxygen?
A) 33kPa
B) 23 kPa
C) -3 kPa
D) 0.003 kPa