**Core Concept**
The question is about calculating the prevalence of a disease in a population, using a 2x2 contingency table or a Venn diagram. Prevalence is the proportion of individuals in a population who have a particular disease at a given time.

**Why the Correct Answer is Right**
To calculate the prevalence, we need to find the total number of individuals with the disease and divide it by the total population. From the table, we see that there are 180 individuals with the disease (true positives) and 20 individuals without the disease but tested positive (false positives), making a total of 200 individuals who tested positive. Similarly, there are 400 individuals without the disease (true negatives). Therefore, the total number of individuals with the disease is 180 (true positives) + 400 (true negatives) = 580. However, the correct approach to calculate the prevalence is to add the true positives and true negatives and subtract the total population that tested positive and negative. The correct calculation is: Prevalence = (180 + 400) / 1000 = 580 / 1000 = 0.58 or 58%. However, this is not the correct answer choice.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not provided in the question.

**Option B:** This option is not provided in the question.

**Option C:** This option is not provided in the question.

**Option D:** This option is not provided in the question.

**Clinical Pearl / High-Yield Fact**
When calculating prevalence, it's essential to remember that prevalence = (true positives + true negatives) / total population, but the correct approach is to add the true positives and true negatives and subtract the total population that tested positive and negative.

**Correct Answer:** **B. 58%**