You’d better __ electricity; it would be dangerous.
My sister,an inexperienced rider,was found sitting on the bicycle _________ to balance it.
_________ in the fields on a March afternoon,he could feel the warmth of spring.
_________ to reach them on the phone,we sent an email instead.
We went right round to the west coast by __________ sea instead of driving across _________ continent.
In____review of 44 studies, American researchers found that men and women ____who ate six key foods daily cut the risk of ______ heart disease by 76%.