What is the clinical importance of mediastinal lymph nodes in animals?

Mediastinal lymph nodes can show signs of septicemia or tuberculosis.
They are always present in all animals.
They are generally small and difficult to locate, but increase in size in response to infectious stimuli.
Caudal mediastinal lymph nodes have clinical importance as they can press the vagus nerve and cause vagal indigestion.
a) Only statements I and IV are correct.
b) Only statements II and III are correct.
c) Statements I, III, and IV are correct.