Samantha's urban community is blanketed with smog. which statement best explains the reason for this poor air quality? people crowd sidewalks as they walk to shopping malls. people use underground subways for long-distance travel. people ride bicycles to commute to work on a daily basis. people drive cars whenever they need to go somewhere.

Explanation:

This poor air quality is due to the excessive use of engine-based transportation like cars. Each person use a single car which emits carbon dioxide, so if there are 1 million of people, would be 1 million of cars emitting this polluting gas, causing the smog.

On the other hand, there are several ways to avoid this, like using subways, bicycles or just walking, all these activities don't contaminate the air, and they will drastically decrease air pollution. The problem nowadays is that people don't want to walk or put any effort to go out, they just want to sit behind the wheel and let the car do all the job, but this way, we aren't gonna have clean air anymore.

what effect does exercise have on the nervous system?

the answer is c.

    however, coronary heart disease , or chd, is actually a result of coronary artery disease, or cad, said edward a. fisher, m.d., ph.d., m.p.h., an american heart association volunteer who is the leon h. charney professor of cardiovascular medicine and also of the marc and ruti bell vascular biology and disease program at the nyu school of medicine.

  with coronary artery disease, plaque first grows within the walls of the coronary arteries until the blood flow to the heart’s muscle is limited. view an illustration of coronary arteries. this is also called ischemia. it may be chronic, narrowing of the coronary artery over time and limiting of the blood supply to part of the muscle. or it can be acute, resulting from a sudden rupture of a plaque and formation of a thrombus or blood clot.

    the traditional risk factors for coronary artery disease are high ldl cholesterol, low hdl cholesterol, high blood pressure, family history, diabetes, smoking, being post-menopausal for women and being older than 45 for men, according to fisher. obesity may also be a risk factor.

    “coronary artery disease begins in childhood, so that by the teenage years, there is evidence that plaques that will stay with us for life are formed in most people,” said fisher, who is former editor of the american heart association journal, atvb. “preventive measures instituted early are thought to have greater lifetime benefits. healthy lifestyles will delay the progression of cad, and there is hope that cad can be regressed before it causes chd.”

  living a healthy lifestyle that incorporates good nutrition, weight management and getting plenty of physical activity can play a big role in avoiding cad.

    “coronary artery disease is preventable,” agreed johnny lee, m.d., president of new york heart associates, and an american heart association volunteer. “typical warning signs are chest pain, shortness of breath, palpitations and even fatigue.” if you feel any of these symptoms, don’t delay — call 9-1-1.