Which of the Following Polynomials Is a Binomial of Degree $3 x ^ { 3 } + 9 x$

Multiple Choice

Which of the following polynomials is a binomial of degree 3?

A) $3 x ^ { 3 } + 9 x$
B) $3 x ^ { 3 } + 9 x ^ { 2 } + 6 x + 2$
C) $3 x ^ { 2 } + 9 x + 6$
D) $3 x ^ { 2 } + 3 x$
E) $3 x ^ { 3 } + 9 x + 6$