What _____ Kathy fell and hurt her knee?[ ]

Do you have any ideas ________ is actually going on in the classroom?

Where are Lucy and Lily?—Oh , the two girls must _______ a game in the garden now.

Where are my keys, Dad? I can’t find them.—- Look! They’re under the table. You must _____.

On which day shall we visit the Fanta Theme Park in Wuhu this week？–. I will be busy this week.