Question

Tobacco smoke contains carbon monoxide, which
A. Reduces the oxygen-carrying capacity of blood
B. Causes gastric ulcers
C. Raises blood pressure
D. Is carcinogenic

Answer 1

The smoke from tobacco contains many chemicals which are harmful to both smokers and non-smokers. Intake of even small amounts of tobacco smoke can be harmful. More than seven thousand chemicals are present in tobacco smoke, in which at least two hundred are known to be harmful which includes hydrogen cyanide, carbon monoxide, and ammonia. Among these known harmful chemicals, at least sixty-nine are known to cause cancer.

Complete answer:
Option A Reduces the oxygen-carrying capacity of blood: Tobacco smoke contains carbon monoxide. The carbon monoxide gas has a greater affinity for hemoglobin than the oxygen. So, when carbon monoxide is present, it binds to hemoglobin and binding of oxygen is reduced. The oxygen cannot bind to hemoglobin as a result and very little oxygen is transported throughout the body.
Hence option A is the correct answer.
Option B Causes gastric ulcers: Open sores which develop on the lining of the stomach are called gastric ulcers or stomach ulcers. They are usually caused by Helicobacter pylori bacteria or non-steroidal anti-inflammatory drugs. Since carbon monoxide from tobacco smoke does not cause gastric ulcers.
Option B is not correct.
Option C Raises blood pressure: The cigarette smoke contains nicotine. Nicotine raises the blood pressure and heart rate and also narrows your arteries and hardens their walls. Tobacco smoke also makes blood more likely to clot. The tobacco smoke stresses the heart and sets up for a heart attack or stroke. Since blood pressure rise is caused due to nicotine in tobacco and not carbon monoxide.
So, option C is not correct.
Option D Is carcinogenic: A mixture of thousands of compounds which includes more than sixty well established carcinogens can be found on a single puff of tobacco smoke. Carcinogens in cigarette smoke belong to multiple chemical classes which includes polycyclic aromatic hydrocarbons, N-nitrosamines, aromatic amines, aldehydes, volatile organic hydrocarbons, and metals. But carbon monoxide is not carcinogenic.
Hence option D is also not correct.

So, Option A. Reducing the oxygen-carrying capacity of blood is the correct answer.

Note:
The tobacco smoke is composed of liquid aerosol droplets particles with a mass median aerodynamic diameter which is sub-micrometer. The droplets are present in high concentrations. Modern cigarettes contain a cigarette filter, which can reduce the tar and nicotine smoke yields up to half the concentration by several different mechanisms, with an even greater removal rate for other classes of compounds such as the phenols.