A 34 year old man was walking along the country side when an insect bit him. After which he started to complain of an annular rash spreading upwards

The key is B. Doxycycline PO. [Described rash is erythema migrans which is characteristic skin lesion

seen in lyme disease. Lyme disease is an infectious disease caused by the bacteria Borrelia burgdorferi

which is spread by ticks. The most common sign of infection is an expanding area of redness on the skin,

known as erythema migrans, that appears at the site of the tick bite about a week after it occurred.

Lyme disease is treated with Doxycycline].