had great difficulty _____the suitable food on the menu in that restaurant.

I came all the way to inform you of the time andplace of the meeting.—You could have _____ yourself the trouble.

Modern forms of transportation and communication have done much to ______ the isolation（隔离）of life in Alaska.

nt research shows that there _____ volcanic activities on the moon and Mars. However, they no longer exist now.

This will not only keep the study habit ____ but also keep you up to date on your class assignments .