Which of these do plants need for photosynthesis to occur? A. glucose and water B. water and oxygen C. water and carbon dioxide D. glucose and carbon dioxide

It's C

Explanation:

It's C because plants need water, sunlight, and carbon dioxide for photosynthesis to occur without these three main concepts plants won't exist

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