Answer:
Option 1 is correct.
Explanation:
There are two types of externality:
(i) Negative externality
(ii) Positive externality
Negative externality:
Suppose there is an economic transaction initiated between the two partners and this transaction reduces the consumption of third person, then this is known as the negative externality.
For example: Smoking is one of the example of negative externality. Smoking a cigarette is not only present in the consumption bundle of a person who smokes but it also affects the health of the other person who stands near that person. So, it reduces the consumption of non smoker.