Final answer:
A respiratory rate of 24 breaths per minute indicates effective oxygen therapy.
Step-by-step explanation:
The assessment finding that will demonstrate that oxygen therapy is effective in a client with shortness of breath receiving 4 L/minute is a) Respiratory rate of 24 breaths per minute. When the respiratory rate is within the normal range, it indicates that the client is able to maintain a sufficient exchange of oxygen and carbon dioxide, suggesting that the oxygen therapy is effective.