Final answer:
The tree with the widest distribution in North America and three needles per bundle is the pine tree, which is an evergreen conifer adapted to cold climates.
Step-by-step explanation:
The tree that is the most widely distributed conifer in North America with three needles per bundle is the pine tree. Pine trees are evergreen coniferous trees that belong to the phylum Coniferophyta and are part of a group known as gymnosperms. They are well-adapted to cold and dry weather due to their needle-shaped leaves with sunken stomata, which limit water loss through transpiration.
These adaptations explain why conifers like pines, spruce, and fir are predominant at high altitudes and in cold climates. Pine needles typically occur in clusters, and the number of needles per cluster is a useful identification aid, with most pines having needles that are longer than 10 cm and occur in bundles of two, three, or five. The correct answer to your question is a. Pine tree.