𝗥𝗲𝗮𝗱 𝗮𝗻𝗱 𝗳𝗶𝗹𝗹 𝗶𝗻 𝘁𝗵𝗲 𝗴𝗮𝗽𝘀.
You _____ do this homework assignment, but those who do will get an extra credit.

• don't have to
• doesn't have to
• could
• mustn't