- How long something lasts is a measure of how long that something is available
- As the use of a resource decreases , the length of time that resource being available will increases
- Hence, as the use of a resource decreases, the length of time that that resource will last increases

- As the use of a resource decreases, the length of time that that resource will last increases
- To last longer means the length of time that something lasts increases
- Hence, decreasing the use of a resource causes that resource to last longer

- Fuel supply is a kind of resource
- Fossil fuels are a kind of energy resource
- Hence, a fossil fuel supply is a kind of resource

- Decreasing the use of a resource causes that resource to last longer
- A fossil fuel supply is a kind of resource
- So, decreasing the use of a fossil fuel supply causes that fossil fuel supply to last longer

- Oil is used for producing electricity
- Oil is a kind of fossil fuel
- Therefore, fossil fuel is used for producing electricity

- Fossil fuel is used for producing electricity
- As the use of something decreases, the use of things used to produce that something decreases
- Therefore, as the use of electricity decreases, the use of fossil fuels decreases

- A supply of something is a source of that something
- As the use of something decreases , the use of the source of that something will decrease
- So, as the use of something decreases, the use of the supply of that something decreases

- As the use of electricity decreases, the use of fossil fuels decreases
- As the use of something decreases, the use of the supply of that something decreases
- Therefore, as the use of electricity decreases, the use of a fossil fuel supply decreases

- Decreasing the use of a fossil fuel supply causes that fossil fuel supply to last longer
- As the use of electricity decreases, the use of a fossil fuel supply decreases
- Therefore, decreasing the use of electricity causes a fossil fuel supply to last longer

- Decreasing the use of electricity causes a fossil fuel supply to last longer
- To decrease something means to reduce something
- Therefore, reducing the use of electricity causes the fossil fuel supply to last longer

Hence, reducing the use of electricity causes the fossil fuel supply to last longer
Question
Which is the best plan to make the fossil fuel supply last longer?

Context
- Oil is used for producing electricity 
- To last longer means the length of time that something lasts increases 
- As the use of something decreases , the use of the source of that something will decrease 
- How long something lasts is a measure of how long that something is available 
- Fossil fuels are a kind of energy resource 
- Oil is a kind of fossil fuel 
- To decrease something means to reduce something 
- As the use of a resource decreases , the length of time that resource being available will increases 
- As the use of something decreases, the use of things used to produce that something decreases 
- Fuel supply is a kind of resource 
- A supply of something is a source of that something