Answer: 
Step-by-step explanation:
Since a Binomial is an algebraic expression of the sum or the difference of two terms.
Therefore, For a binomial an expression must contain exactly two terms.
In a)
there is only one term therefore it is not the Binomial.
In a)
, there is only one term therefore it is not the Binomial.
In a)
there is exactly two terms therefore it is a Binomial.
In a)
there are three terms therefore it is not the Binomial.