Advantages of greenhill

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.

the answer is:  

line graphs show patterns in data with variables that change over time; whereas, circle graphs show data as parts out of a whole (such as out of 100%).

oxygen, selenium, tellurium, and polonium.

they're all from the same group as sulfur (group 16).