What is the condition in which an odorless gas combines rapidly with hemoglobin and crowds out oxygen?

The correct answer is - carbon monoxide poisoning.

Explanation:

Carbon monoxide poisoning is the condition which is involves the combining rapidly with hemoglobin with a odorless gas and crowds out or reduction of the oxygen.

Carbon monoxide or CO is a odorless gas can be present in various fumes exhaust from the tobacco smoke or cars. it joins with the hemoglobin like oxygen not let go.

Thus, the correct answer is - carbon monoxide poisoning.