The most common source of carbon monoxide pollution is vehicle exhaust.

The Carbon monoxide (CO) is a colorless, odorless, tasteless, and toxic air pollutant. It is produced in the incomplete combustion of carbon-containing fuels, such as gasoline, natural gas, oil, coal, and wood. The largest anthropogenic source of CO in the United States is vehicle emissions. When we breathe high concentrations of CO leads to reduced oxygen (O2) transport by hemoglobin and with are able to get health effects

How how am i supposed to know

Pretty sure this would be b. the rest are trick questions. the bystanders  won't go near you if u have cpr cuffs that could hurt them. the dog will back off because the sound will scare him. and the vomits just a stupid trick. if there is that much slober and vomit on the guy hes either choking on it, or just take off his shirt.