Hi, there.
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Let me start by defining a binomial.
A binomial is an expression with 2 terms. These could be variables, constants, they could have any exponents, but as long as that expression has 2 terms, it's considered a binomial.
Of the 4 choices provided, which one shows an expression with 2 terms?
Only C.

Hope the answer - and explanation - made sense,
happy studying!!!