1£®There is no doubt ________ only by lifelong learning can we keep up with the advancing society.

2£®As is well known, ________  matters most in learning English is enough practice.

3£®The manager put up a notice to keep the staff informed of what  ________ (do)this week.

4. ________ (sleep)late in the morning£¬Bob turned off the alarm.

5£®There was a time ________ he was disappointed and wanted to leave here.

6. ________ can be easily proved that nothing is more important than friendship.

7£®The Nile River used to flood large areas but now the water is used  ________ (produce) electricity.