An adult inhales about 6.0 times 10^-4 m^3 of fresh air during a breath. Only 20% of fresh air is oxygen. Assume the pressure in the lungs is 1.0 times 10^5 Pa and the air is at a temperature of 300 K. How many oxygen molecules are in each breath? 2.9 times 10^21 4.9 times 10^-4 2.9 times 10^25 1.4 times 10^23