单项选择题
A．to describe how pruning a tree is done B．to discuss different ways of pruning trees C．to give practical instructions for pruning a tree D．to explain how a tree wound gets diseased and heals
A. infers B. prefers C. refers D. defers
A．During a storm, lightning damaged cable. B．Because of unemployment. C．Heat waves had made people use too much electrical power. D．Because the looters damaged the electricity supply.