How many polynomials are there in the following expressions:  $$-4{{x}^{2}}+2$$，$$-\frac{1}{3}mn$$，$$ \pi $$，$$\frac{{{(2x-y)}^{2}}}{3}$$，$$32\frac{1}{4}$$~ ~． 
选项为:A:$$1$$  B:$$2$$  C:$$3$$  D:$$4$$  请回答其中一个选项.