How many of the following functions are Binomial probability mass functions?

i.$p(x)={30 \choose x} p^x(1-p)^{15-x}$ for $x=0,1,2,\ldots,15$

ii.$p(x)=p^x(1-p)^{1-x}$ for $x=0,1$

iii.$p(x)={10 \choose 5} p^5(1-p)^{10-5}$

iv.$p(x)={5 \choose x}p^x(1-p)^{5-x}$ for $0\leq x\leq5$

v.$p(x)=\dfrac{2!}{x!(2-x)!}p^x(1-p)^{2-x}$ for $x=0,1,2$