1. While working in the country, the students_____ a great deal of knowledge on plant.
A. looked up B. picked up C. put up D. called up
2. Was it in the village ______ he was born ______ the talented journalist met the retired professor?
A. that, where B. where, which C. which, where D. where, that
3. What difficulty will you have _______ people when you stay in a foreign country?
A. understanding B. understood C. to understand D. understand
