The correct matching of the vitamins (List I) with their corresponding deficiency diseases (List II) is as follows:

A. Ascorbic acid (Vitamin C) - III. Bleeding of Gums B. Vitamin D - II. Osteomalacia C. Riboflavin (Vitamin B2) - IV. Cheilosis D. Vitamin A - I. Xerophthalmia

The given options associate different vitamins with their corresponding deficiency symptoms. Let's elaborate on each of these associations:

A. Ascorbic acid (Vitamin C) - III. Bleeding of Gums

•  A deficiency of vitamin C, also known as ascorbic acid, can lead to a condition known as scurvy. 

B. Vitamin D - II. Osteomalacia

•  A deficiency of vitamin D can lead to a condition called osteomalacia in adults. 

C. Riboflavin (Vitamin B2) - IV. Cheilosis

• A deficiency of riboflavin, which is also known as vitamin B2, can lead to a condition called cheilosis. 

D. Vitamin A - I. Xerophthalmia

• A deficiency of vitamin A can lead to a condition known as xerophthalmia, which is a serious eye disorder. 

In summary, each of these associations correctly links a specific vitamin with its corresponding deficiency symptom. These associations highlight the importance of a balanced diet to ensure an adequate intake of essential vitamins and prevent the development of deficiency-related health issues.

So, the correct answer is:

3.A-III, B-II, C-IV, D-I