Select the part whose main job is to break down sugar to release energy that a plant cell can use.

Mitochondria

Explanation:it breaks down the glucose and release energy in the form of ATP adenosine tri phosphate

hydrogen is a compound or a single element and a element is a pure substence that cannot be separated into simpler subtances

clorine is a compound its a chemical substance that forms when two or more different elements combine

so both hydrogen and clorine are compounds