Final answer:
When administering Penicillin for strep throat, the nurse should monitor for skin rash/hives as they can signify an allergic reaction, which might lead to anaphylaxis.
Step-by-step explanation:
The nurse administering Penicillin for a patient with strep throat should be vigilant for signs of an acute allergic reaction. Among the options provided, the correct adverse effect to look for is c. skin rash/hives. These are symptoms that can indicate an allergic reaction, which in severe cases can escalate to anaphylaxis, a life-threatening condition characterized by a significant release of histamines leading to symptoms such as swelling of the tongue and throat, drop in blood pressure, and difficulty breathing.