Read the following passage and answer the questions that follow:
"Smog, a term coined 50 years ago, from the words "Smoke" and "fog" is a dirty yellow-brown cloudy formation in lower portion of troposphere near the ground. Smog, we are most familiar with are Los Angles and London smog. Former is a example of photochemical smog, and later is a classical smog which contained sulphur dioxide, sulphur trioxide, sulphuric acid, heavy suspended particles, and water vapours. Los Angles smog was formed by photochemical reactions among nitrogen oxides and volatile hydrocarbons in presence of sunlight. This type of smog contains ozone, PAN, formaldehyde, and causes eye irritation, impairs pulmonary functions and damage plants and crops."