-What are you worried about?-Tom didn't respond ______ any of my e-mails. Something must have happened to him.
He always lacks enthusiasm in work,and he's never ________a job for longer than a few weeks.
Spending so much time playing computer games is holding him ________at school.
We thought of selling this old furniture,but we've decided to ________it. It might be valuable.
________a moment and I will go to your rescue.
He's so determined that no one can ________from making an attempt.