Please turn off the stove. The water ________ for more than fifteen minutes.

     A. is boiling               B. was boiling         C. has been boiling D. will be boiling

In the 19th century, it ________ two or three months to cross North America by covered wagon. The trip ________ very rough and often dangerous.

I ________ the same car for more than ten years. I ________ about buying a new one.

They ________ good preparations before they ________ their final examination yesterday.

- I called you last night after dinner, but you were not there. Where ________?

     - I ________ overtime at the fitness center.

Those drivers ________ for three hours when a heavy storm suddenly ________

I ________ a mystery movie on TV when the electricity ________ out.

My best friend and I ________ each other for over fifteen years. We still ________ together once a week.