Ans. is 'b' i.e., Antibiotic treatment of contacts Close contacts of persons with confirmed meningococcal disease are at an increased risk of developing meningococcal illness.Antibiotics are effective in preventing additional cases through eradicating carriage of the invasive strain.Most secondary case occur within the first 72 hours after presentation of the index case; risk of secondary disease decreases to near baseline by 10-14 days.Antibiotics effective for this purpose include rifampicin, ciprofloxacin, ceftriaxone or azithromycin.