Visitors________not to touch the exhibits.
Everyone here will thank the firefighters for the things they do to prevent fires ______ the environment safer.
If Newton lived today, he would be surprised by what ______ in science and technology.
Does John know any other foreign language ______ English?
Life is just like a journey with ______ unknown destination, during which people can meet with ______ barriers of all kinds.
After that, she knew she could __________ any difficulties by doing what she could to the best of her ability.