This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Bacteriology, Subject name: Microbiology
A patient presents with fever, cough with sputum and weight loss. He has a history of not completing treatment for tuberculosis thrice in the past. XDR-TB is suspected. How is XDR-Tb defined? 
Select and explain. 
A. Resistant to INH + Rifampicin + Amikacin, B. Resistant to INH + Amikacin + Ofloxacin + Ethambutol, C. Resistant to INH + Rifampicin + Amikacin + Ofloxacin, D. Resistant to Rifampicin + Amikacin+ Ofloxacin
C: Resistant to INH + Rifampicin + Amikacin + Ofloxacin
Answer: C: Resistant to INH + Rifampicin + Amikacin + Ofloxacin 
Explanation: XDR-TB (Extensively drug-resistant TB) is defined as MDR TB (Resistant to rifampicin and isoniazid) + Resistant to one fluoroquinolone (eg. ofloxacin) + resistance to one injectable second line drug (Amikacin or kanamycin or capreomycin). Reference: Ananthanarayan and Paniker&;s Textbook of Microbiology Tenth edition