This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Microbiology
Which among the following is known as 'Eaton agent' which causes respiratory infection? 
Select and explain. 
A. Corynebacterium, B. Pseudomonas, C. Mycoplasma, D. Streptococcus
C: Mycoplasma
Answer: C: Mycoplasma 
Explanation: M. pneumoniae pneumonia is also referred to as Eaton agent pneumonia (the organism having first been isolated in the early 1940s by Monroe Eaton), primary atypical pneumonia, and "walking" pneumonia. A mild tracheobronchitis with fever, cough, headache, and malaise is the most common syndrome associated with acute M pneumoniae infection. The pneumonia is typically less severe than other bacterial pneumonias. It has been described as "walking" pneumonia because most cases do not require hospitalization. Ref: Hardy R.D. (2012). Chapter 175. Infections Due to Mycoplasmas. In D.L. Longo, A.S. Fauci, D.L. Kasper, S.L. Hauser, J.L. Jameson, J. Loscalzo (Eds), Harrison's Principles of Internal Medicine, 18e.