There are many types of natural selection like direct selection, disruptive selection and stabilizing selection.
The situation given is that a population of mice lives in a city. The largest mice tend to be killed by predators and the smallest mice cannot compete for food.
The type of selection here is stabilizing selection. It is a type of natural selection in which there is decrease in genetic diversity as the population stabilizes.
I'd also say that the morphology presented in this picture is filamentous.
The reason for my believing this is that filamentous morphology concerns long visible chains, threads, or filaments, which you can see in the image.
A- Temperature.
Hope this helps!<span />