Finnish Translation
Vesi koostuu hapesta ja vedystä.
Since the word “of” is there, the cloze needs to be “consists” (or “is made [up]”, although this language pair doesn’t have any multi-word clozes).
“Comprise” means exactly the same thing as “consist of” (or “unite into a whole”). It would be correct to write “Water comprises oxygen and hydrogen”—WITHOUT the “of”—but there’s no way to make “comprise” work in the current incarnation of this sentence. (“Water is comprised of…” is a popular mistake, but a mistake nonetheless.)