Classify the following object as a mammal, a fish, a reptile, or a bird: Humpback whale.
The Humpback whale is a mammal.
Complete the following task based on the instruction and optional input provided.### Instruction:
Classify the following object as a mammal, a fish, a reptile, or a bird: Humpback whale.

### Output:
The Humpback whale is a mammal.