Scientists still wonder whether cloning will help or harm us and where it ____ us.
He has lived at____ for 30 years.
The book is of great value ____ can be enjoyed form it until you have a deep understanding of it, however.
One of the sides of the board should be painted yellow, and ______. .
---You don’t often see them, do you? ---No, I see ______of them.
He is clever and hard-working, so he has _____ reason to succeed in the exam.