## Core Concept
The question pertains to the epidemiology of cancer, specifically focusing on the most common type of cancer that results in death. This involves understanding the global cancer burden and the mortality rates associated with different types of cancer.

## Why the Correct Answer is Right
Lung cancer is widely recognized as the leading cause of cancer deaths globally. This is primarily due to its high incidence and mortality rates. The majority of lung cancer cases are associated with smoking, which is a significant risk factor. The high mortality rate of lung cancer can be attributed to its often late diagnosis and the aggressive nature of the disease.

## Why Each Wrong Option is Incorrect
* **Option A:** While breast cancer is one of the most common cancers in women and can be fatal if not detected early, it is not the leading cause of cancer deaths when considering all genders.
* **Option B:** Colorectal cancer is common but does not have as high a mortality rate as lung cancer, mainly because it often presents with symptoms that lead to earlier detection.
* **Option C:** Although prostate cancer is prevalent among men, its mortality rate is lower compared to lung cancer, partly due to the generally slower progression of the disease.

## Clinical Pearl / High-Yield Fact
A crucial point to remember is that smoking cessation programs are critical in reducing the incidence and mortality of lung cancer. The implementation of anti-smoking policies has been shown to decrease the rates of smoking and subsequently the incidence of smoking-related cancers.

## Correct Answer Line
**Correct Answer: D. Lung cancer**.