Propose how a scientist might support a hypothesis that rocks from one quarry were formed at the same time as rocks from another quarry 50 km away

A method to determine this is correlation (matching of unique rock fossils exposed in one geographic region to similar fossils exposed in other geographic regions).

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).

and your question what topic are you in trouble with?