Do you think yesterday’s math problem was difficult? —Yes. I could ________ work it out.
Who is the girl standing over there? —Well, if you _____ know, her name is Kate.
I don’t know what ________ of students in that school is, but you can see there are _________ of bikes and e-bikes outside the gate.
What will the weather be like tomorrow? –It____ be rainy, cloudy or sunny. Who knows?
I don’t know if he_______ tomorrow. If he _______, I will call you.