The correct answer is prey predator relationship.
The given graph possibly shows the prey predator relationship, in which the prey is shown in red and the predator is shown in blue. It is observed that the predator population generally remain less than the prey, in order to get food easily.
The prey predator relationship shows that if the population of the prey start increasing, then the population of the predator would also increase, as the predators have abundant of food. But when the population of the prey start decreasing, the predators start to decline due to the starvation.
B. A species that does not normally live in an area
Dozens of tower cranes dot DC's skyline, and so many of them are building new high-rise apartments that the District now ranks ninth among US cities with the most housing units under construction. It sure looks like a lot of new housing supply is being built, and certainly plenty of new luxury apartments within the District. However, the downtown high-rises under construction only tell half the story of Greater Washington's housing growth story.
While all those cranes are easy to see from afar, what isn't immediately apparent from the airport (but might be from a plane) is that many fewer acres of the countryside around us are being bulldozed for subdivisions–which for the past century has been where most lower-cost, low-rise housing was built. As a result, the region as a whole isn't building enough housing for our rising population.
Reducing sprawl is good, but we haven't built enough housing in city cores to meet demand
Fewer than half as many single-family houses are being built at the suburban fringes of Greater Washington every year, compared to the region's long-range average. Taken together, the single-family houses that aren't being built around Greater Washington each year would cover four square miles–an area the size of Rock Creek Park. The slower pace of suburban development over the past ten years has meant tens of thousands of acres of farms and forests around our region haven't been bulldozed for subdivisions and strip malls.
