Match the following:
(i) Riboflavin            (a) Beriberi
(ii) Thiamine            (b) Scurvy
(iii) Pyridoxine        (c) Cheilosis
(iv) Ascorbic acid    (d) Convulsions

We begin by recalling the standard list of vitamins, their chemical names and the classical deficiency diseases associated with each of them. Knowing these fixed pairings allows us to match each item in the left column with the corresponding disease in the right column.

First, consider $$\text{Riboflavin}$$, which is commonly known as Vitamin B2. A deficiency of Vitamin B2 typically produces lesions at the corners of the mouth, a condition medically termed cheilosis. Hence we match

$$\text{Riboflavin}\; \longrightarrow \; \text{Cheilosis} \; (c).$$

Next, look at $$\text{Thiamine}$$, or Vitamin B1. The classical deficiency disease here is beriberi, which affects the nervous and cardiovascular systems. Therefore we set up the correspondence

$$\text{Thiamine}\; \longrightarrow \; \text{Beriberi} \; (a).$$

Now we move to $$\text{Pyridoxine}$$, better known as Vitamin B6. Lack of this vitamin often manifests as neurological disturbances such as irritability and, in severe cases, convulsions. Thus we write

$$\text{Pyridoxine}\; \longrightarrow \; \text{Convulsions} \; (d).$$

Finally, $$\text{Ascorbic acid}$$ is simply Vitamin C. Its deficiency leads to defective collagen synthesis, giving rise to the well-known disease scurvy. We therefore pair

$$\text{Ascorbic acid}\; \longrightarrow \; \text{Scurvy} \; (b).$$

Collecting all four matched pairs, we have

$$ \begin{aligned} (i)&\; \text{Riboflavin} &\longrightarrow&\; (c)&\; \text{Cheilosis},\\ (ii)&\; \text{Thiamine} &\longrightarrow&\; (a)&\; \text{Beriberi},\\ (iii)&\; \text{Pyridoxine} &\longrightarrow&\; (d)&\; \text{Convulsions},\\ (iv)&\; \text{Ascorbic acid} &\longrightarrow&\; (b)&\; \text{Scurvy}. \end{aligned} $$

Comparing this ordered set with the answer choices, we see that it matches exactly with Option C, which states (i)-(c), (ii)-(a), (iii)-(d), (iv)-(b).

Hence, the correct answer is Option C.