## Core Concept
The question compares the calcium content in different types of milk. Calcium content in milk can vary depending on the source (e.g., cow, goat, sheep) and type (e.g., whole, skimmed, condensed).

## Why the Correct Answer is Right
Goat's milk has a similar calcium content to cow's milk, with approximately 8-9 mg/mL. Sheep's milk has a higher calcium content compared to cow's and goat's milk, around 10-11 mg/mL. Buffalo milk also has a high calcium content, similar to or slightly higher than sheep's milk. However, **skimmed milk** or more accurately, the type of milk with the lowest calcium content among common types would generally be related to processing rather than the source. Among the given options, if we consider common types and processing effects, **skimmed milk** might not necessarily have the lowest calcium content inherently; however, watered-down or very processed milks could have lower concentrations. Typically, though, cow's milk (whole) has about 9 mg/mL of calcium.

## Why Each Wrong Option is Incorrect
- **Option A:** This option cannot be evaluated without specific details but assuming standard types of milk, cow's milk has a well-established calcium content.
- **Option B:** Similarly, without specifics, it's hard to evaluate, but if it represents another common type like goat or sheep, their calcium contents are known to be high.
- **Option C:** This would be incorrect based on the correct answer but without specifics on types, it's a placeholder for an incorrect option.
- **Option D:** Buffalo milk is known for its high nutrient content, including calcium, making it an unlikely candidate for the lowest calcium content.

## Clinical Pearl / High-Yield Fact
A key point to remember is that **fortified plant-based milks** (like soy milk or almond milk) can have varying calcium contents depending on fortification, often ranging widely but can be made to match or exceed dairy milk's calcium content.

## Correct Answer: .