Jennifer Aniston offered to cook dinner for me tonight, therefore, I won't get takeout on the way home. Do I need to Fix any punctuation or capitalization errors ^

Everything look's good, I would say there's nothing to fix. The comma's are properly placed, her name is capitalized and you finished with a period.

where is the

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).