For adults 18 and older, a normal resting heart rate is between 60 and 100 beats per minute (bpm), depending on the person's physical condition and age.
B. 50-60%....the true recommendation is 45-65% but since that is not an option I would go with choice B
The main components of smog are nitrogen oxides,
volatile organic compounds, peroxyacytyl nitrate and tropospheric ozone. Smog
is a mixture of air pollutants which are altered due to exposure to sunlight.