In his rear-view mirror Raju sees the roof sign of the car behind exactly as shown. Which panel shows the sign as it really is?

Reflect the image left-to-right again. Every letter of the sign is symmetric, so the letters themselves do not change, but their order is reversed back: the real sign reads TAXI: (d). (a) keeps the mirror order I X A T, while (b) and (c) are upside down.