Neither Tom nor Jack and I ______his students, but each of us _____ gone to the hospital to see him.
. About 71% of the earth’s surface ______ covered with water, but 20% of the world population ______ have access to safe drinking water.
. — Have you thought of a theme for your poster yet? — No, I ______ a lot about it, but I haven’t decided.
. ______ left before the deadline, it doesn’t seem likely that John will finish the job.
. Medical ______ shows that men are more likely to have heart attacks than women.
. Several years had passed ______ I finally realized the true value of friendship.