Which of the following contains lactic acid?

Options

A. ant's sting
B. unripe grapes
C. lemons
D. sour milk

Answer

To determine which of the options contains lactic acid, we can analyze each option provided in the question. Here’s a step-by-step solution:

### Step 1: Understand what lactic acid is
Lactic acid is an organic acid that is produced in the body during anaerobic respiration. It is also found in certain foods, particularly fermented products.

### Step 2: Analyze the options
1. **Ant stings**: Ant stings contain formic acid (also known as methanoic acid), which causes a burning sensation. This does not contain lactic acid.

2. **Unripe grapes**: These contain tartaric acid and citric acid. Tartaric acid is responsible for the sour taste in grapes, but they do not contain lactic acid.

3. **Sour milk**: Sour milk is produced through fermentation, where bacteria such as Lactobacillus convert lactose (the sugar in milk) into lactic acid. Therefore, sour milk is a source of lactic acid.

4. **Other options**: If there are any other options, we would analyze them similarly, but based on the provided information, sour milk is the only one that contains lactic acid.

### Conclusion
The correct answer is **sour milk**, as it contains lactic acid produced by the fermentation process.

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