A sample of oxygen gas is collected over water at 23 Celsius at a barometric pressure of 751mmHg (the vapor pressure of water at 23 Celsius = 21mmHg). The partial pressure of oxygen gas in the sample collected is:
A. 44mmHg
B. 21mmHg
C. 751mmHg
D. 1.02atm
E. 0.96atm