A.
Example,
While John was lying on his bed, Jack was outside playing soccer.
Delete usual. Custom and usual do not flow together and a custom is already a usual thing, just like tradition.
Answer:
<em>Overcrowded and poor living conditions can contribute to the spread of airborne diseases such as tuberculosis and respiratory infections such as pneumonia. Reliance on open fires or traditional stoves can lead to deadly indoor air pollution. A lack of food, clean water and sanitation can also be fatal.</em>
