A client with a history of heart failure is examined in the outpatient department to investigate the recent onset of peripheral edema and increased shortness of breath. Physical findings include bilateral crackles, a third heart sound (S3), distended neck veins, elevated blood pressure, and pitting edema of the ankles. The nurse documents the severity of pitting edema as +1. What is the best description of this type of edema（）
A. Barely detectable depression when the thumb is released from the swollen area; normal foot and leg contours.
B. Detectable depression of less than 5 mm when the thumb is released from the swollen area; normal foot and leg contours.
C. A 5-to 10-mm depression when the thumb is released from the swollen area; foot and leg swelling.
D. A depression of more than 1 cm when the thumb is released from the swollen area; severe foot and leg swelling.