Final answer:
To display a score on the Scratch stage, you check the box next to the score variable in the variable's block palette.
Step-by-step explanation:
To display a score on the screen in Scratch, the correct answer is C: check the box next to it. This is referring to the checkbox that appears next to variables in the Scratch interface. When you create a variable in Scratch, like a score variable, and you want it to show up on the stage, you simply check the box next to the variable in the block palette. This will create a small monitor display on the stage that shows the current value of your variable, such as the player's score in a game.