**Core Concept**
The attributable risk, also known as the risk difference, measures the proportion of disease incidence that can be attributed to a specific risk factor. In the context of cervical cancer, it estimates the increased risk of developing the disease due to exposure to multiple sex partners.

**Why the Correct Answer is Right**
The attributable risk is calculated as the difference between the risk of disease in the exposed group and the risk of disease in the unexposed group. In this scenario, the exposed group is the one with multiple sex partners, and the unexposed group is assumed to have no sex partners. The risk of cervical cancer in the exposed group is 5 times higher than in the unexposed group. Therefore, the attributable risk is the difference between the risk in the exposed group and the risk in the unexposed group, which is calculated as (5 - 1) / 5 = 4 / 5 = 0.8 or 80%.

**Why Each Wrong Option is Incorrect**
* **Option A:** Not provided, skipping.
* **Option B:** This option is not relevant to the calculation of attributable risk, which is a measure of the proportion of disease incidence attributed to a specific risk factor.
* **Option C:** This option is incorrect because it does not represent the correct calculation of attributable risk.
* **Option D:** This option is incorrect because it does not represent the correct calculation of attributable risk.

**Clinical Pearl / High-Yield Fact**
When calculating attributable risk, it's essential to remember that the risk in the exposed group is compared to the risk in the unexposed group. This is a key concept in epidemiology and is often tested in medical exams.

**Correct Answer: C. 0.8 or 80%**