A 5-year-old child is brought to the hospital with the complaint of fever, cough, breathlessness and chest pain. On examination he is found to be dull, but irritable with fast pulse (116/min), rapid breathing (RR 50/min) and indrawing of lower chest during inspiration, wheezing, crepitations and mild dehydration. Body temperature is 40°C (104°F). The paediatrician makes a provisional diagnosis of acute pneumonia and orders relevant haematological as well as bacteriological investigations. He decides to institute antibiotic therapy.In case he selects an antibiotic which can be given orally as well as by i.m. or i.v. injection,which route of administration will be most appropriate in this case?