A basket of vegetable contains carrot, potato, radish and tomato. Which one of the following represents correct homologus structures?

Question

$\begin{array}{1 1} (a)\; \text{Carrot and Potato} \\ (b)\; \text{Carrot and Tomato} \\ (c)\; \text{Radish and Carrot} \\ (d)\; \text{Radish and Potato} \end{array}$