Which of the following statements is not true about ecosystems?

1. a healthy ecosystem can support an unlimited number of life forms.
2. the parts of an ecosystem depend on each other.
3. predators play a role in balancing the earth's ecosystems.
4. people's activities can improve the health of an ecosystem.

Imagine a self-reactive t cell that has not undergone clonal deletion in the thymus (that is to say, it has escaped central tolerance). if it encounters self antigen in the absence of an infection or inflammation, what will happen to this self-reactive t cell? (select two answers) (a) the t cell undergoes clonal expansion. (b) the t cell gains effector functions. (c) the t cell undergoes apoptosis. (d) the t cell becomes activated. (e) the t cell becomes anergic.