**Question:** The percentage of pulmonary emboli, that proceed to infarction, is approximately-

A. 20%
B. 40%
C. 60%
D. 80%

**Core Concept:**
Pulmonary embolism (PE) is a life-threatening condition characterized by the blockage of pulmonary artery branches by blood clots. Depending on the size and location of the clot, it can lead to various degrees of lung tissue damage and eventual infarction (death of tissue due to lack of blood supply).

**Why the Correct Answer is Right:**
The correct answer (D) represents the approximate percentage of pulmonary emboli that can progress to infarction, which is defined as an irreversible injury or death of lung tissue due to the blockage of blood flow. In the majority of cases, the clot's size, location, and the patient's underlying conditions (e.g., venous stasis, hypercoagulable state) determine the severity and likelihood of infarction.

**Why Each Wrong Option is Incorrect:**
A) 20% is too low, considering that larger or more massive emboli are more likely to cause infarction.
B) 40% is too high, as not all emboli will lead to infarction.
C) 60% is close to the correct answer D, but still too high due to the various factors influencing the progression to infarction.

**Clinical Pearl:**
A PE can be categorized as either small, intermediate, or large based on the size of the clot. Small clots are less likely to cause infarction, while larger clots have a higher likelihood of causing infarction due to their potential to occlude more pulmonary arteries, leading to a more significant reduction in blood flow and oxygenation.

**Correct Answer:** 80%