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
True about Diptheria -a) Caused by Gram negative bacillib) Incubation period 2-5 daysc) Chemoprophylaxis is done with rifampicind) Previously immunized asymptomatic household contact should receive booster dosee) Child recovered from illness- give active immunization 
Select and explain. 
A. c, B. d, C. ab, D. bd
D: bd
Answer: D: bd 
Explanation: None