You can never imagine what great difficulty I have _____ your house.

I knocked on the door but ________ answered.

. – ______Bob be the manager of our company? – He ______ be, but I’m not sure.

---How does your English teacher help you to practice English?--- By encouraging us to __________ some dialogues with our partner in class.

It was a real race        time to get the project done. Luckily, we made it.