【单选题】

The pines belong to the coniferous (结球果的) class of trees; that is, trees which bear cones. The pines may be told from the other coniferous trees by their leaves, which are in the form of needles two inches or more in length. These needles keep green throughout the entire year. This is characteristic of all coniferous trees, except the larch and cypress, which shed their leaves in winter.

The pines are widely distributed throughout the Northern Hemisphere, and include about 80 distinct species with over 600 varieties. The species enumerated here are especially common in the eastern part of the United States, growing either native in the forest or under cultivation in the parks. The pines form a very important class of timber trees and produce beautiful effects when planted in groups in the parks.
How to tell them from each other: The pine needles are arranged in clusters.Each species has a certain characteristic number of needles to the cluster and this fact generally provides the simplest and most direct way of distinguishing the different pines.
In the white pine there are five needles to each cluster, in the pitch pine three, and in the Scotch pine two. TheAustrian pine also has two needles to the cluster, but the difference in size and character of the needles will distinguish this species from the Scotch pine.
Which of the following trait is common to pine trees
A、They differ among themselves by shades of green.
B、Their pine needles are arranged in clusters.
C、They are most common to the western United States.
D、They have different numbers of branches.