What is the purpose of stage directions? to provide comic relief after various pivotal and tense moments in a play and lighten the mood of the audience to set up the backdrop of a play by providing background information on the characters to break a play down into multiple scenes according to changes in locations to describe details about where a scene takes place and how an actor must deliver his or her lines

the following key ideas correctly express the key sentence.

restate key idea: most people can learn to swim in ten short lessons.

restate key idea: the majority of water-accident victims require mouth-to-mouth breathing.

restate key idea: an empty, tightly closed gallon jug will support a tired swimmer.  

restate key idea: first aid is to prevent accidents as well as assist in rescue.

explanation: the key idea needs to have the same topic as the key sentence (drowning and safety).