The spokesman was very ______ about expressing his opinions in public in case he might make mistakes.
China has long been a leader in the field of genetic research ________ improving agriculture.
You lent him $10,000 yesterday? You must ________ by him!
— How do you find the food here? — _______.
Elizabeth _______ a good plan of increasing sales at the meeting.
The woman ________ Mr. Brown is a professor from Beijing University.