— I wonder why he has been acting so strange these days.—Recent pressure at work may_____ his behavior.
If you______the right map , we wouldn’t have got lost.
—Which umbrella can I take? —You can take______of them; I will use none.
Living in the desert involves a lot of problems,______water shortage is the worst.
Only when you have obtained enough data______ come to a sound conclusion.
Lessons______easily are soon forgotten.