What does an iamb is a unit of poetry consists of

Well it´s actually easier than you imagine.

Explanation: It´s just a short and weak (unnstressed) syllable, followed by a contrapart: a long and strong (stressed) syllable.

Take a moment to consider and think about how useful the application of this concept could be. It basically marks the rhtyhm of how poetry works. If it´s a walk through the park, jogging in the stadium or running for your life.

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).