Smoking reduces the amount of oxygen available for diffusion at the lungs, so less oxygen gets absorbed and blood is oxygenated to a lesser degree.  Having read the above passage, choose the right answer to the following question (choices are more or less ):   Will is smoking a cigarette. This causes more or less oxygen to be available for diffusion in his lungs, so less oxygen will be absorbed into his blood?
The answer to this question is:
less