ジョンはもう職業を決めましたか。

topic marker particle; indicates contrast with another option (stated or unstated); adds emphasis

now; soon; shortly; before long; presently; already; yet; by now; (not) anymore; further; more; again; another; the other; interjection used to strengthen expression of an emotion (often exasperation)

occupation; business

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 decide; to choose; to determine; to make up one's mind; to resolve; to set one's heart on; to settle; to arrange; to set; to appoint; to fix; to clinch (a victory); to decide (the outcome of a match); to persist in doing; to go through with; to always do; to have made a habit of; to take for granted; to assume; to dress up; to dress to kill; to dress to the nines; to carry out successfully (a move in sports, a pose in dance, etc.); to succeed in doing; to immobilize with a double-arm lock (in sumo, judo, etc.); to eat or drink something; to take illegal drugs

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