Context: They can go pretty fast on a flat road but any kind of hill and they obviously slow down . Ever overtaken one of these things ? Only then would you know how it plays with your nerves to start with !

Question: Why might these slow down on any kind of hills ?
Options:
0. These things might slow down on hills because they 're overpowered .
1. None of the above choices .
2. These things might slow down on flat roads because they 're underpowered .
3. These things might slow down on hills because they 're underpowered .
Answer: 3