Read the passage below and choose the best answer that expresses the main idea of the passage:
People concerned with the environment and global warming usually try to reduce their carbon output by increasing
their home’s energy efficiency and driving less. Some start by calculating their carbon footprint to set a benchmark —
like a weigh-in before a diet. A carbon footprint is simply a figure — usually a monthly or annual total of CO2 output
measured in tons.
Everyone should reduce their carbon
C. People concerned with global warming
should know their carbon footprint so they
will know how they can reduce their carbon
d. Everyone puts out tons of CO2 into the
atmosphere every day,
b. You should always calculate your carbon
footprint before going on a diet.