A client hospitalized with a pneumothorax

问题：

A client hospitalized with a pneumothorax has the following arterial blood gas (ABG) analysis: pH, 7.19; partial pressure of arterial carbon dioxide (PaCO₂), 63 mmHg; and,22 mEq/L. A chest tube was inserted and oxygen administered at 4 L/min by nasal cannula. One hour after the initiation of treatment, ABG analysis reveals: pH, 7.28; PaCO₂, 52 mmHg; and ,22 mEq/L. This change in ABG analysis indicates（）

A. respiratory alkalosis.

B. impending respiratory arrest.

C. the need for intubation.

D. improved respiratory status.