.I don't remember how many years ago ______ people began to grow crops.
Please say "Hi" to Bob ______ me.
After we walked ______ the forest, and ______ a river, we arrived at that small village.
We were about to leave the classroom _____ it began to rain.
Three students in ten will go and _____ to stay in the classroom.
The beef is too expensive. I won’t buy it _____.