Which characteristic is shared by all living things? having the ability to communicate being composed of one or more cells being able to breathe air the tendency to live in groups

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

i believe your answer would be c.. : )