Name a selective weed killer.

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for the name of a selective weed killer. Selective weed killers are designed to target specific types of plants (weeds) without harming desirable plants, such as grass.

2. **Definition of Selective Weed Killer**: A selective weed killer is a type of herbicide that effectively kills weeds while leaving other plants unharmed. This is particularly useful in maintaining lawns and sports fields.

3. **Identifying an Example**: One well-known example of a selective weed killer is 2,4-Dichloro-Phenoxyacetic Acid, commonly referred to as 2,4-D. This compound is widely used in agriculture and landscaping to control broadleaf weeds.

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