Density of population tells us about :

number of individuals present per unit space in a given time

The correct answer is Option (3) –number of individuals present per unit space in a given time

 Population density is a measure of the number of individuals of a species per unit area or volume in a given time. It provides an indication of how crowded or sparse a population is within a specific habitat, which is important for understanding ecological dynamics, resource availability, and the potential for interactions among individuals. Birth rate and immigration increases population density while death rate and emigration decreases population density in an area.

Population density tells you how crowded an area is, on average. It can help in figuring out the resources that a certain area requires. The formula for calculating the population density is:

Population Density = Number of People / Land Area.