Find the Term That Should Be Added to the Expression $x^{2}+3 x$

Multiple Choice

Find the term that should be added to the expression to form a perfect square trinomial. Write the resulting perfect square trinomial in factored form.
- $x^{2}+3 x$

A) $0 ;(x+3) ^{2}$
B) $\frac{9}{4} ;\left(x+\frac{3}{2}\right) ^{2}$
C) $\frac{9}{4} ;\left(x-\frac{3}{2}\right) ^{2}$
D) 0 ; $\left(x+\frac{3}{2}\right) ^{2}$