Final answer:
The correct phrase is 'The pair of scissors is placed on the table', because 'pair' is a singular collective noun.
Step-by-step explanation:
The correct answer to this question is 'The pair of scissors is placed on the table.' This is the correct formation because 'pair' is a collective noun that refers to two of something, but it is singular in form, so it uses singular verbs. Analogous to this, saying 'The team is scoring' or 'The couple argues'. So, regardless of the fact that there are two objects involved (in this case, the two blades of the scissors), we still use the singular verb 'is' instead of 'are' because 'pair' is singular.
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