Refer to the chart below showing the major threats for plants, mammals, and birds that are considered vulnerable to extinction.

-What is the biggest threat, and why?

A) Intrinsic factors, because they have a big impact on threatened mammals
B) Direct loss/exploitation, because it affects both mammals and birds
C) Alien invasive species, because they have a big impact on threatened birds
D) Habitat loss/degradation, because it has the most impact on all three groups
E) Natural disasters, since they are the most unpredictable