Hãy chọn biểu thức đúng biểu diễn tín hiệu theo phần thực và phần ảo

$X\left(e{}^{j\omega }\right)=\sqrt{\text{R}\text{e}{}^2\left[X\left(e{}^{j\omega }\right)\right]+j\text{I}\text{m}{}^2\left[X\left(e{}^{j\omega }\right)\right]}$

$X\left(e{}^{j\omega }\right)=\text{R}\text{e}\left[X\left(e{}^{j\omega }\right)\right]+\text{I}\text{m}\left[X\left(e{}^{j\omega }\right)\right]$

$X\left(e{}^{j\omega }\right)=\text{R}\text{e}\left[X\left(e{}^{j\omega }\right)\right]+j\text{I}\text{m}\left[X\left(e{}^{j\omega }\right)\right]$

$X\left(e{}^{j\omega }\right)=\sqrt{\text{R}\text{e}\left[X\left(e{}^{j\omega }\right)\right]+\text{I}\text{m}\left[X\left(e{}^{j\omega }\right)\right]}$