If a policymaker wants to reduce the level of CO2 emissions, policy should target energy and transportation.deforestation and agriculture.agriculture and land use.waste and land use.

Energy and transportation.

Step 1: Understanding CO2 Emissions Carbon dioxide (CO2) emissions are primarily produced by burning fossil fuels, such as coal, oil, and natural gas. This happens in various sectors, including energy production, transportation, industry, and residential use.

Step 2: Identifying Major Sources of CO2 Emissions Among the options given, the energy and transportation sectors are the largest sources of CO2 emissions. Energy production, especially from coal and natural gas, is the largest single source of global CO2 emissions. The transportation sector, which includes cars, trucks, planes, and ships, is also a significant source of CO2 emissions.

Step 3: Targeting Policy Therefore, if a policymaker wants to reduce the level of CO2 emissions, policy should target the energy and transportation sectors. This could include policies to promote renewable energy, improve energy efficiency, and encourage the use of electric or hybrid vehicles.

So, the answer to the question "If a policymaker wants to reduce the level of CO2 emissions, policy should target" is Energy and transportation.