Shortly after being admitted to the coronary care unit with an acute myocardial infarction (MI), a client reports midsternal chest pain radiating down the left arm. The nurse notices that the client is restless and slightly diaphoretic, and measures a temperature of 99. 6°F (37.6℃), a heart rate of 102 beats/minute; regular, slightly labored respirations at 26 breaths/minute; and a blood pressure of 150/90mmHg. Which nursing diagnosis takes highest priority ？（）
A．Risk for imbalanced body temperature.
B．Decreased cardiac output.
C．Anxiety.
D．Acute pain.
