Because they will grow really long if you don't
Finches recognise individuals of their species based on appearance and songs. More specifically, finches differences in appearance that they can recognise include the body colour, size and shape. Concerning the songs that they sing, they are significant differences between the song that each species sing.
The answer is D: poaching, since it harms wildlife and destroys ecosystems.
A pathogen is a disease carrying vector that has the ability to spread using a variety of different mechanisms. A pathogen that is a contagion has the ability to spread through touch. An example of such a pathogen would be the one that results in staph infections.