Why was 1990 an important year regarding air quality? select two options.
the united states took first steps to keep the air clean.
cost-effective ways to reduce pollution were emphasized.
the united states created the environmental protection agency.
modifications and improvements were made to the clean air act.
funding was established under the clean air act to study air pollution.

Radiometric dating is used to tell the absolute age of materials by studying the decay rate of radioactive isotopes. the decay rates of isotopes are constant and are expressed as .

When in solution, a molecule that moves slowly across an artificial membrane moves rapidly across a plasma membrane. this molecule rapidly enters the cell regardless of whether its concentration is higher inside or outside the cell. using this information, which transport mechanism is most likely to be responsible for the movement of the molecule across a plasma membrane? view available hint(s)when in solution, a molecule that moves slowly across an artificial membrane moves rapidly across a plasma membrane. this molecule rapidly enters the cell regardless of whether its concentration is higher inside or outside the cell. using this information, which transport mechanism is most likely to be responsible for the movement of the molecule across a plasma membrane? active transportexocytosis

7. describe two strategies that parents can use to cope with stress. 8. describe the three types of childcare available to families. 9. what can parents do to be more involved in their children's education at home and at school? 10. which factors should a parent consider when choosing a childcare option?