$\"\"$

Consider the second expression is $\"\"$ .

The product a sum and a difference formula: $\"\"$ .

The product of these binomials is a difference of two squares and does not have a middle term.

Consider the remaining expressions are $\"\"$ .

The square of a sum formula: $\"\"$ .

The square of a difference formula: $\"\"$ .

The product of these binomials is a sum of two squares and do have a middle term. $\"\"$

The expression $\"\"$ does not belong.