It has been known since ancient times that people behave oddly when the moon is full. the moon's gravity may be the cause.
which sentence could be added to complete the summary?

what is your question?

1. the relationship between a pronoun and its antecedent- reference

reference refers to the relationship between mainly pronoun and another unit of grammar- noun phrase or noun.

2. a singular noun naming a collection or group- collective noun.

collective noun refers to the kind of noun which refer to the name of people, thing or anything in collective. for instance bundle of sticks, herein 'bundle' is collective noun.  

3. a modifying clause whose subject and/or verb is implied- elliptical clause

it is a clause in which words are being left out. on the other hand, the missing word is understood due to the logic or pattern of the sentence.  

4. two or more nouns and/or pronouns serving the same grammatical function and followed by a pronoun that references one or all nouns- compound antecedent

compound antecedent refers to which is made up of two or more words which are joined by 'or' or 'and.'

5. an adjective clause introduced by a pronoun- relative clause.

relative clauses are the clauses which begin with the relative pronouns such as when, where, which, that or who. the noun that precedes, relative pronouns identify or define that noun.  

6. the word, phrase, or clause to which a pronoun refers- antecedent.

antecedents refers to the phrases, clauses or words which are replaced with one of the third personal pronouns.

i recommend hoot, and paper towns

answer :

the idiom "pride goes before a fall" means that being too proud causes one to make mistakes that eventually lead to failure or downfall.

in the stranger's story in the "the storyteller," bertha had won three medals for obedience, punctuality and good manners. she was really proud of her medals and pinned them to her dress and wore them everywhere she went so that everyone would know how good she was. in the end, these symbols of her excessive pride cost her her life. when she was hiding from the wolf in the bushes, it was the clinking of her medals that alerted his attention towards her presence and lead to her death.