Which would most likely be hotter in the northern hemisphere a cloudy day in july or a sunny day in july

the answer is a or when it says crossing over

"d.) carbon dioxide and hydrogen sulfide"

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

you can have just about every answer you can think of