Which of the following is a characteristic of emphysema?

Assertion $(A):$ $A$ person goes to high altitude and experiences 'altitude sickness' with symptoms like breathing difficulty and heart palpitations.
Reason $(R):$ Due to low atmospheric pressure at high altitude,the body does not get sufficient oxygen.
In the light of the above statements,choose the correct answer from the options given below.

If the level of carboxyhaemoglobin in blood reaches up to......,the functioning of the central nervous system is severely affected,which results in death.

Tobacco smoke contains carbon monoxide,which

What is the cause of lung cancer in coal miners?

The increase in the incidence of asthma during certain seasons is primarily due to: