The professor, ________ his assistants, _______ conducting the experiment.
All the Harry Potter books by Joanne Rowling, a poor single mother ________ in Edinburgh, ________ all over the world.
—Lily is going to make a presentation in class this afternoon.—Oh, really? I ________ it was Michael's turn.
The house is dirty because it ________ since they moved out.
Now we have arrived at the lake. But the view I photographed that day ________ any more.
Up to now, our society ________ with limited living space and a shortage of natural resources.