In this task, you are given a multiple-choice question about healthcare. Answer the question based on your information and classify your answers into '1', '2', '3', and '4'.
Q: Question: CO is toxic to aerobic organisms:
Options: <1> Because it oxidizes the OH groups of the hemoglobin, preventing it from being able to fix O2 correctly. <2> Because it enters the mitochondria, picking up electrons from the transport chain with less efficiency than O2. <3> Because it joins the heme group with greater affinity than O2. <4> Because having a greater dipolar character, is more soluble than O2 in blood and blocks the exchange of O2 between air and blood at the level of the lungs. <5> None of the above is correct.
A:
3