read the following passage and answer the following questions.
Polychlorinated Biphenyls (PCBs) are a special type of waste that are found throughout the world in water, sediments, bird tissues, and fish tissue. They are made by substituting 1 to 10 chlorine atoms onto the biphenyl aryl structure. They have very high chemical, thermal, and biological stability, low vapour pressure, and high dielectric constants. These properties have led to the use of PCBs as coolant insulation fluids in transformers and capacitors; for the impregnation of cotton and asbestos; as plasticizers; and as additives to some epoxy paints. However, the very same properties have contributed to their widespread dispersion and accumulation in the environment. But, some degree of biodegradation of PCBs in the environment does occur. Substitutes of PCBs for electrical applications have been developed. Disposal of PCBs from discarded electrical equipment and other sources have caused problems, particularly since PCBs can survive ordinary incineration by escaping as vapours through the smokestack. However, they can be destroyed by special incineration processes.

The number of benzene rings in PCBs is:

1

2

3

4

Solution

Correct option is B

Polychlorinated Biphenyls (PCBs) consist of two benzene rings connected by a single carbon-carbon bond. These rings can have up to 10 chlorine atoms substituted at various positions. The general structure of PCBs is C₁₂H₁₀₋ₓClₓ, where x represents the number of chlorine atoms.
The presence of these two benzene rings contributes to the chemical stability and persistence of PCBs, making them resistant to degradation.
Information Booster: 1. PCBs are made of biphenyl molecules, which means two benzene rings joined together.
2. They can have 1 to 10 chlorine atoms substituted on these rings.
3. The structure makes PCBs non-polar and insoluble in water, leading to bioaccumulation in fats.
4. The stability of these rings gives PCBs their high dielectric constant, making them suitable for electrical uses.
5. The environmental persistence of PCBs is linked to their chemical structure and chlorine substitutions.