"Each" is used when referring to individual members of a group, emphasizing them one at a time. Here, it appropriately refers to the individual sections being described.

"Every" is generally used to refer to all members of a group as a whole but does not fit well in this context, as we are focusing on individual sections.

"Both" is incorrect because there are three sections, not two.

"All of the above" cannot be correct because "both" is not suitable in this sentence.