- Pollution has a negative impact on the environment / air quality / water quality / society
- Solar energy rarely causes pollution
- Hence, solar energy rarely has a negative impact on the environment

- Solar energy rarely has a negative impact on the environment
- Harming something has a negative impact on / effect on that something
- Hence, solar energy rarely harms the environment

- Solar energy rarely harms the environment
- If something happens rarely then that something likely happens the least
- So, solar energy likely harms the environment the least

- Solar energy likely harms the environment the least
- Solar energy is a source of electricity
- Hence, solar energy is a source of electricity that likely harms the environment the least

- Solar energy is a source of electricity that likely harms the environment the least
- Solar power means solar energy
- Therefore, solar power is a source of electricity that likely harms the environment the least

Therefore, solar power is a source of electricity that likely harms the environment the least
Q: Which source of electricity would harm the environment the least?
Context:
- Pollution has a negative impact on the environment / air quality / water quality / society 
- Solar energy is a source of electricity 
- If something happens rarely then that something likely happens the least 
- Solar power means solar energy 
- Solar energy rarely causes pollution 
- Harming something has a negative impact on / effect on that something