誰がホームランを打ったのですか。

who

indicates sentence subject (occasionally object); indicates possessive (esp. in literary expressions); but; however; still; and

home run

indicates direct object of action; indicates subject of causative expression; indicates an area traversed; indicates time (period) over which action takes place; indicates point of departure or separation of action; indicates object of desire, like, hate, etc.

to hit; to strike; to knock; to beat; to punch; to slap; to tap; to bang; to clap; to pound; to strike (noon, etc.); to sound (cymbals, etc.); to beat (a drum, etc.); to beat (rhythmically, e.g. pulse, waves, etc.); to move; to impress; to touch; to drive in; to hammer in; to put in; to inject; to type; to send; to transmit; to insert; to write in; to mark; to make (noodles, etc.); to prepare; to till (soil); to sprinkle; to throw; to cast; to do; to carry out; to play; to perform; to engage in (gambling, etc.); to pay (a deposit, etc.); to visit (on a pilgrimage); to line (a coat); to bind (a criminal)

indicates possessive; nominalizes verbs and adjectives; substitutes for "ga" in subordinate phrases; (at sentence-end, falling tone) indicates a confident conclusion; (at sentence-end) indicates emotional emphasis; (at sentence-end, rising tone) indicates question

be; is

indicates a question (sometimes rhetorical); or; whether or not; some- (e.g. something, someone); indicates doubt, uncertainty, etc.; emphatic prefix; suffix forming adjectives or adverbs; in that way