**Core Concept**
The concept being tested is the relationship between mean and median in a dataset. The mean is the average value of a set of numbers, calculated by summing all the values and dividing by the total count. The median is the middle value when the data is arranged in ascending or descending order. This concept is crucial in understanding data distribution and is often used in statistical analysis.

**Why the Correct Answer is Right**
When the mean is less than the median, it indicates that the dataset is skewed to the left. This means that the majority of the data points are concentrated on the right side of the distribution, with a few extreme values pulling the mean down. In such cases, the median is a more representative measure of central tendency. This is because the median is less affected by extreme values and provides a better estimate of the typical value in the dataset.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe the relationship between mean and median. A negative skew is characterized by a long tail on the left side of the distribution, which is not what we are discussing here.

**Option B:** This option is incorrect because it describes a right-skewed distribution, where the mean is greater than the median. This is the opposite of what we are discussing.

**Option C:** This option is incorrect because it does not accurately describe the relationship between mean and median. A bimodal distribution is characterized by two distinct peaks, which is not relevant to the concept being tested.

**Clinical Pearl / High-Yield Fact**
Remember that in a left-skewed distribution, the mean is pulled down by extreme values, making it a less reliable measure of central tendency. In such cases, the median is a better choice.

**Correct Answer:** D. Skewed to the left.