- If something comes from something else then that something else is a source of that something
- Oil is a source of gasoline
- So, gasoline comes from oil

- Gasoline comes from oil
- Oil is a nonrenewable resource
- Hence, gasoline comes from a nonrenewable resource

- Gasoline comes from a nonrenewable resource
- A nonrenewable resource is limited in supply
- Therefore, gasoline comes from a resource that is limited in supply

- For something to be replaced means for something else to be used instead of that something
- If a resource is limited in supply then that resource needs to be replaced
- Hence, if a resource is limited in supply then something else needs to be used instead of that resource

- Gasoline comes from a resource that is limited in supply
- If a resource is limited in supply then something else needs to be used instead of that resource
- A limited resource means a resource that is limited in supply
- Hence, something else must be used instead of gasoline because gasoline comes from a limited resource

- An automobile is a kind of vehicle
- Vehicles usually require gasoline to operate
- Hence, automobiles usually require gasoline to operate

- Automobiles usually require gasoline to operate
- Alternative fuels are being used in some automobiles
- Therefore, alternative fuels are being used in some automobiles instead of gasoline

- Something else must be used instead of gasoline because gasoline comes from a limited resource
- Alternative fuels are being used in some automobiles instead of gasoline
- Therefore, alternative fuels are being used instead of gasoline in automobiles because gasoline comes from a limited resource

Therefore, alternative fuels are being used instead of gasoline in automobiles because gasoline comes from a limited resource
Why are alternative fuels being used in some automobiles?
- An automobile is a kind of vehicle 
- Vehicles usually require gasoline to operate 
- If something comes from something else then that something else is a source of that something 
- Oil is a source of gasoline 
- A nonrenewable resource is limited in supply 
- Oil is a nonrenewable resource 
- Alternative fuels are being used in some automobiles 
- For something to be replaced means for something else to be used instead of that something 
- If a resource is limited in supply then that resource needs to be replaced 
- A limited resource means a resource that is limited in supply