They ______ on the program for almost one week before I joined them, and now we _____on it as no good results have come out so far.

—Have you received your new shoes? —Yes. And at the same time I got the jacket I _____. 

The ambulance was just arriving, for a worker, who ______ the window on the second floor, fell off the window.

—Why were you so late this morning? —I _____ in heavy traffic for an hour on the way here.

North Korea threatens to ________ from six-party talks aimed at ending North Korea's nuclear program unless its proper rights are to be satisfied．