Which of the following animals are mammals ?
Elephant, snake, hen, cow, lizard, monkey, peacock, cockroach, whale.

Explanation

To determine which of the following animals are mammals, we can follow these steps:

### Step 1: Understand the Characteristics of Mammals
Mammals are defined by certain key characteristics:
- They produce young ones (live births in most cases).
- They possess mammary glands, which allow them to feed their young with milk.
- Their bodies are typically covered with hair or fur.

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