First there is a cell, and a bunch of cells make up tissues, and a bunch of tissues makes up an organ, which makes up a organ system (like the digestive system), which makes up a organism.
Molecule is more of a chemistry thing, so it's not included in Biology, the smallest unit of life is a cell.
The answer is (A) as <span> increasing risk of lung cancer is from increasing levels of exposure to outdoor air pollution and </span>particulate matter
