Fact 1: Invertebrates are animals that lack a vertebral column, or backbone. Fact 2: Invertebrates are animals without backbones, and vertebrates are animals with backbones. Given the two facts above, what do vertebrates have?

Select from:
1). tails.
2). strength.
3). eardrum.
4). heart.
5). brain.
6). Chlorophyll.
7). back bone.
8). stamina.
The answer is:
7).