Fact 1: Some touch receptors sense differences in temperature or pain. Fact 2: Merkel's discs are touch receptors. Given the two facts above, what sense differences in temperature or pain?

Available options:
1). Veins and arteries.
2). the skin
3). Merkel's discs
4). movie discs
5). frontal zones
6). cd discs
7). sensory neurons
8). sound discs
The answer is:
3).