Final answer:
Conifers encompass a variety of tree species including pines, spruces, and firs. They are adapted to cold climates and are used for timber and paper pulp. The correct option is d.
Step-by-step explanation:
Conifers, which belong to the phylum Coniferophyta, include a variety of evergreen and a few deciduous trees. Species such as pines, spruces, and firs are all part of this diverse group of gymnosperms. These trees are particularly adapted to cold and dry climates due to their needle-shaped leaves with sunken stomata and waxy cuticles which help to reduce water loss. Conifers are dominant in cold environments, and high altitudes, and are commonly used for timber and paper pulp due to their 'softwood' quality.