When _____ to danger and conflict, men tend to increase blood pressure, _____ nervous and anxious.

Chengdu has focused on improving the surrounding countryside，________encouraging large-scale city expansion.

How are you getting on with your work? — I can’t do it __________ any longer.I will have to get help.

Listen ! Helen is singing in the next room.It ____ be Helen. She has gone to Beijing.

I will try to avoid ___ the same mistake.