Insert articles where necessary: Vitamins are essential ingredients of ... food but are only needed in minute quantities. There are many different vitamins but ... most important for examination purposes are vitamins B, C and D.
Vitamin B is really ... complex of related vitamins found in cereals and liver. They take part in ... production of energy from digested food and in ... formation of red blood cells.. Deficiency may cause ... anaemia.
Vitamin C, found in fresh fruit and vegetables, is necessary for the formation of capilary blood vessels. Deficiency leads to bleeding and ... gum disorders.
Vitamin D is present in ... meat fat, fish and dairy products. It is necessary for bone and tooth formation and ... deficiency may affect their structure.

Vitamins are essential ingredients of our food but are only needed in minute quantities. There are many different vitamins but the most important for examination purposes are vitamins B, C, and D.

Vitamin B is really a complex of related vitamins found in cereals and liver. They take part in the production of energy from digested food and in the formation of red blood cells. Deficiency may cause anaemia.

Vitamin C, found in fresh fruit and vegetables, is necessary for the formation of capillary blood vessels. Deficiency leads to bleeding and gum disorders.

Vitamin D is present in meat fat, fish, and dairy products. It is necessary for bone and tooth formation and a deficiency may affect their structure.

Now, let's insert the necessary articles in the given sentences:

1. Vitamins are essential ingredients of our food but are only needed in minute quantities.
Explanation: Here, the article "our" is added before the noun "food" to show that we are talking about the food we consume.

2. There are many different vitamins but the most important for examination purposes are vitamins B, C, and D.
Explanation: The definite article "the" is used before the superlative adjective "most important" to specify which vitamins we are referring to.

3. Vitamin B is really a complex of related vitamins found in cereals and liver.
Explanation: The indefinite article "a" is used before the noun "complex" as we are referring to one of the complexes of related vitamins.

4. They take part in the production of energy from digested food and in the formation of red blood cells.
Explanation: No article is needed before the nouns "production" and "formation" as they are referring to general activities.

5. Deficiency may cause anaemia.
Explanation: The indefinite article "a" is used before the noun "anaemia" as we are talking about one possible result of deficiency.

6. Vitamin C, found in fresh fruit and vegetables, is necessary for the formation of capillary blood vessels.
Explanation: No article is needed before the noun "formation" as it is referring to a general process.

7. Deficiency leads to bleeding and gum disorders.
Explanation: No article is needed before the nouns "bleeding" and "gum disorders" as they are referring to general conditions.

8. Vitamin D is present in meat fat, fish, and dairy products.
Explanation: No article is needed before the nouns "meat fat," "fish," and "dairy products" as they are referring to general categories of food.

9. It is necessary for bone and tooth formation and a deficiency may affect their structure.
Explanation: No article is needed before the nouns "bone" and "tooth" as they are referring to general structure. The definite article "the" is used before "deficiency" as it refers to a specific deficiency in this context.