Final answer:
The client demonstrates an understanding of the teaching when they state they will complete the full course of antibiotics as prescribed, which is essential to fully eradicate the infection and prevent antibiotic resistance.
Step-by-step explanation:
The correct statement by the client that indicates an understanding of the nurse's teaching on amoxicillin-clavulanate for treating pharyngitis is C) “I'll complete the full course of antibiotics as prescribed.” A patient must complete the full course of antibiotics even if they feel better before the end of the regimen. Doing so ensures that all the bacteria causing the infection are killed and reduces the risk of developing antibiotic-resistant strains of the bacteria. Sharing medication with others (D) is not advised since prescriptions are individualized and what works for one person may not be appropriate or safe for another. Discontinuing medication prematurely (B) can lead to a resurgence of the infection and contribute to antibiotic resistance. Only taking antibiotics when symptoms worsen (A) is not a correct approach, as it can lead to incomplete treatment and potentially worsen the condition.