Assertion (A): Smoking leads to availability of less oxygen to the body.
Reason (R): In presence of CO, O2 binds less with Hb.
1. Both (A) and (R) are true and (R) is the correct explanation of (A).
2. Both (A) and (R) are true but (R) is not the correct explanation of (A).
3. (A) is true but (R) is false.
4. Both (A) and (R) are false.