If $P=\left\{x\in R:f\left(x\right)=0\right\}$ and $Q=\left\{x\in R:g\left(x\right)=0\right\}$ then $P\cup Q$ is

• A

  $\left\{x\in R:f\left(x\right)+g\left(x\right)=0\right\}$

• B

  $\left\{x\in R:f\left(x\right).g\left(x\right)=0\right\}$

• C

  $\left\{x\in R;{\left(f\left(x\right)\right)}^2+{\left(g\left(x\right)\right)}^2=0\right\}$

• D

  $\left\{x\in R;x>1\right\}$