Concept:High population density intensifies competition for limited resources like jobs, housing, and public services.
Explanation:High population density means many people live closely in a small area.
As a result, the number of job seekers becomes much higher than the available jobs.
This severe competition for limited employment opportunities leads to unemployment.
Unemployment is therefore a major social and economic disadvantage of high population density.
The other options describe positive effects, not disadvantages.
A low crime rate is an advantage of effective social control.
Low pressure on social amenities is an advantage because facilities are not overused.
Regular flow of traffic is also an advantage since it indicates smooth movement of vehicles.
Only unemployment clearly shows the negative consequence of too many people competing for too few resources.
Answer:A. Unemployment