Which sentence uses the word effect correctly

1. how does the storm effect the crops?
2. which was the major effect of the civil war?
3. i know that my decision will effect my grade.
4. the dog attack will effect the leash laws in city park.

the leaf is an organ of a typical plant, and the main functions are to complete photosynthesis and allow the plant to exchange gas, just like how we have the respiratory system. leaves have the stomata, which collects maintains co2 and o2 levels. this is necessary for cell metabolism. the leaf also collects sunlight using chloroplasts. succinctly, leaves own a pivotal role in sustaining plant life.