Questions

A data dictionary is a special file that contains a set of information describing the contents, format, and structure of a database and the relationship between its elements, used to control access to and manipulation of the database.

The process of conversion of milk into curd is called fermentation.  It is a chemical change. Milk consists of globular proteins called casein. As the microorganism lactobacillus react with milk and turn it to curd. For it 37 degree temperature is needed. But sometimes when it does not get favourable condition, then other microorganism react and makes the curd taste different.

Central Processing Unit (CPU) is the brain of any computer system.

Nitrogenous base: A molecule that contains nitrogen and has the chemical properties of a base.

DNA and RNA ::

The nitrogenous bases in DNA are

Adenine (A),

Guanine (G),

Thymine (T), and

Cytosine (C).

Whereas the nitrogenous bases in RNA are the same, with one exception:

Adenine (A),

Guanine (G),

Uracil (U), and

Cytosine (C).

Here Homologous Means having the same relation or relative position or structure. 

Here in snakes poison is in glands and here salivary glands are in Vertebrates.

Water has the maximum density at 4oC. So at this temperature, it sinks down to bottom and stays here. If it cools further, it will become less dense and move up. So while the upper layers can cool enough to form ice, the bottom layers remain as water at  4oC .  

Therefore, (C) is correct.