My sister,an inexperienced rider,was found sitting on the bicycle _________ to balance it.
__________ warm at night, I would fill the woodstove, and then set my alarm clock for midnight so I could refill it.
I stopped the car __________ a short break as I was feeling tired.
Volunteering gives you a chance __________ lives, including your own.
I cannot __________ puzzled, for I simply cannot understand how I could have made such a stupid mistake.
-I hear Mr. Black is ill in hospital again. -What a poor man ! I can't help but __________ sorry for him.