ANS:A - NH₂.CO.NH₂

Urea is represented as NH2.CO.NH2. Urea is an organic compound with the chemical formula CO(NH2)2. In the chemical formula, the nitrogen atom is bonded to two amine groups (-NH2) and a carbonyl group (-CO-). Therefore, the correct representation of urea is NH2.CO.NH2. The representation NH2.CO.NH2 corresponds to the structural formula of urea, a simple organic compound with the chemical formula CO(NH2)2. This representation indicates the arrangement of atoms within the molecule. Here's an explanation of each part of the representation:

• NH2: This represents the amine functional group, consisting of a nitrogen atom bonded to two hydrogen atoms. Urea has two of these NH2 groups.
• CO: This represents the carbonyl group, which consists of a carbon atom double-bonded to an oxygen atom. This group is often found in organic compounds, particularly those derived from carboxylic acids. In urea, the central carbon atom in the carbonyl group is bonded to the nitrogen atoms from the NH2 groups.
• NH2: This is another amine group, similar to the one mentioned earlier. Urea has two NH2 groups, one on each side of the carbonyl group.

Therefore, NH2.CO.NH2 represents the arrangement of one carbonyl group sandwiched between two amine groups in the urea molecule. This arrangement allows urea to participate in various chemical reactions and interactions, making it a versatile compound used in many industrial and biological processes, including as a fertilizer and in the synthesis of other organic compounds.