a b c d

a

$V_{rms} = \frac{\int_0^\frac{T}{4}{V^2dt}}{\frac{T}{4}}$ $ V = \frac{4V_0}{T} t$ $V_{rms} = \frac{\int_0^\frac{T}{4}{(\frac{4V_0}{T} t)^2dt}}{\frac{T}{4}} = \frac{V_0}{\sqrt 3}$