$33.$ A voltage waveform is shown below, please find its RMS voltage value. Choose the value that is closest to the answer.

$($a$)0\mathrm{.}5$ V

$($b$)1\mathrm{.}0$ V

$($c$)3\mathrm{.}87$ V

$($d$)2\mathrm{.}0$ V

$($e$)2\mathrm{.}45$ V