A：f(x+y)=f(x)f(y)

B：$f\left(x-y\right)=\frac{f\left(x\right)}{f\left(y\right)}$

C： $f\left(nx\right)={f\left(x\right)}^n\left(n\in Q\right)$

D：$f{\left(xy\right)}^n={f\left(x\right)}^n{f\left(y\right)}^n\left(n\in N^{+}\right)$