Answer:
Option (a) is correct.
Step-by-step explanation:
Externality is the consequence of an activity which affects the third party either in a positive way or in a negative way.
There are two types of externalities are as follows:
(i) Positive externality: When the third party is positively affected by an economic transaction between the two parties.
(ii) Negative externality: When the third party is negatively affected by an economic transaction between the two parties.
In our case, there is an increase in the level of pollution created by Singapore which results in an increase in the global warming. This will affect the whole world in a negatively manner and also affect their level of GDP.