The accepted value for the density of iron is 7.9 g/mL. Which of the following sets of experimental data for the density of iron is the most precise?
A) Group 1: 7.98 g/mL, 7.85 g/mL
B) Group 2: 7.65 g/mL, 7.64 g/mL
C) Group 3: 7.03 g/mL, 8.54 g/mL
D) Group 4: 5.43 g/mL, 5.47 g/mL

Harry lives in a city, and he has a lung condition known as asthma. on certain days, harry has to stay inside because pollutants in the air make it difficult for him to breathe. which of these pollution sources are nonpoint sources that might bother harry if he goes outside? choose the two that apply.