Substance a doesn't have fixed melting and boiling points substance b has fixed melting and can't be broken down by chemical reaction substance c has fixed melting and boiling points and breaks down into simpler substances when heated

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 awnser is group 12