The correct meaning for the idiom "The ball is in your court" is B: It is your decision. This idiomatic expression is commonly used to indicate that it is someone's turn to take action or make a decision, and the responsibility for the next step now rests with them. It implies that a previous action or statement has been made, and now the onus is on the other person to respond or proceed.
The phrase originates from sports, particularly tennis, where after a player hits the ball over the net, it is then "in the other player's court," meaning it's their turn to hit it back. This metaphor perfectly conveys the idea of responsibility shifting from one person to another.
For instance, if you've presented a proposal to a client and they've reviewed it, you might say, "The ball is in your court now," meaning it's up to them to decide whether to accept it or not. It emphasizes that the next move is theirs.