Can anyone tell me which part is considering as reasons “why government should impose a sugar tax”, and which parts is telling us why government should not impose a sugar tax?

what do you mean

explanation:

to inform the reader that the text will take a second look at the grimms’ original tales

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).