--- I didn’t go to class last night because my car broke down.  --- You _______ mine. I wasn’t using it. 

—What's the matter with the man hanging his head there?—Well，if you ________ know, he was caught stealing my bike. 

It’s required that mineral resources_______ hand in hand with the local environment protection.

—“What courses are you going to take next semester if you want to receive enough credits to get your degree?”—“I don’t know. But it’s about time      on something.”

It is hard for me to imagine what I would be doing today if I ____ in love, at the age of seven, with the Melinda Cox Library in my hometown.