Answer: D
S81.84 is the correct code for this case because it codes for puncture wounds with a foreign body of the lower leg. Here, this is the diagnosis where the nail is the foreign body.
Option A is not correct because S81.81 is used to code for laceration without foreign body of lower leg. Here, the nail is the foreign body and the wound is a puncture wound.
Option B is not correct because S81.82 is used to code for laceration with a foreign body in the lower leg of the body. Here, the wound is a puncture wound.
Option C is not correct because S81.83 is used to code for puncture wounds without a foreign body of the lower leg.