Final answer:
It is true that canines have the longest roots, aiding in their tearing function, and that third molars have the shortest crowns due to space limitations in the jaw.
Step-by-step explanation:
When comparing crown lengths to root lengths, it is true that the canines have the longest roots, whereas the third molars (wisdom teeth) have the shortest crowns. Canines are designed for tearing food and hence have longer roots to provide the necessary support for their function. Third molars, or wisdom teeth, typically have less room to develop, which can lead to them being impacted or having shorter crowns when they do erupt.