One day you wake with a sore throat and a runny nose. Your doctor takes a swab from your throat, sends it to a lab, and telephones you the next day to say that antibiotic will not help you get better. Which of the following is the most likely reason for the doctor's statement?

• Having waited a day, it is too late to take an antibiotic
• You need an antiseptic, not an antibiotic
• You need to be vaccinated instead of taking an antibiotic
• You are infected by a virus