**Core Concept**
The odds ratio (OR) is a measure of association between an exposure and an outcome, calculated as the ratio of the odds of the exposed group to the odds of the unexposed group. In epidemiological studies, the OR is used to quantify the strength of the association between a risk factor (such as smoking) and a disease (such as lung cancer).

**Why the Correct Answer is Right**
To calculate the odds ratio, we use the following formula: OR = (a/b) / (c/d), where a is the number of exposed cases, b is the number of unexposed cases, c is the number of exposed controls, and d is the number of unexposed controls. In this scenario, a = 75 (smokers with lung cancer), b = 15 (non-smokers with lung cancer), c = 40 (smokers without lung cancer), and d = 60 (non-smokers without lung cancer). Plugging in these values, we get OR = (75/15) / (40/60).

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not provided.
**Option B:** This option is not provided.
**Option C:** This option is not provided.
**Option D:** This option is not provided.

**Clinical Pearl / High-Yield Fact**
When calculating the odds ratio, it's essential to ensure that the data are presented in a 2x2 contingency table format, with the exposed group and unexposed group in the rows, and the cases and controls in the columns. This format helps to avoid errors in calculation.

**Correct Answer: 2.83**