**Core Concept**
The ankle-brachial index (ABI) is a critical measure used in vascular surgery to assess peripheral arterial disease (PAD). It is the ratio of the systolic blood pressure at the ankle to the systolic blood pressure in the upper arm (brachium). A normal ABI value indicates healthy blood flow to the lower extremities.

**Why the Correct Answer is Right**
The correct answer, **B. 1**, reflects a normal ABI value, which suggests that the blood pressure at the ankle is equal to the blood pressure in the upper arm. This is because the ABI is calculated by dividing the highest ankle systolic pressure by the highest brachial systolic pressure. A value of 1 indicates that there is no significant obstruction in the blood vessels supplying the lower extremities. In contrast, values below 1 may indicate PAD, while values above 1 may indicate non-compressible calcified arteries.

**Why Each Wrong Option is Incorrect**
**Option A:** A value of 0.8 would indicate mild PAD, as the blood pressure at the ankle is lower than the blood pressure in the upper arm, suggesting some degree of arterial obstruction.

**Option C:** A value of 1.2 would indicate non-compressible calcified arteries, as the blood pressure at the ankle is higher than the blood pressure in the upper arm, suggesting that the arteries are stiff and unable to compress.

**Option D:** A value of 1.4 would also indicate non-compressible calcified arteries, similar to option C, with an even greater discrepancy between the blood pressure at the ankle and the upper arm.

**Clinical Pearl / High-Yield Fact**
It is essential to note that ABI values can be influenced by various factors, including smoking, diabetes, and hypertension. A low ABI value can be an independent predictor of cardiovascular events and mortality.

**✓ Correct Answer: B. 1. The ankle-brachial index is a ratio of systolic blood pressures between the ankle and upper arm, with a normal value of 1 indicating healthy blood flow to the lower extremities.**