The most common variety of softwood tree east of the cascades is a. douglas fir b. juniper c. pine d. aspen

The most common variety of softwood tree east of the cascades is Douglas fir

Explanation:

The Douglas-firs ranges form the size of medium to large. They grow around twenty to hundred meters.  The Douglas-firs has flatter and softer leafs. Their leafs are two to four cms in length. It will be very easier to find these trees. The branches that are in the lower side of the trees will be lost when the tree grows.

The place where there an existence of these trees will have bright light as the branches of these trees will be very close to the ground surface. These trees are found more in the east edge of Cascades. They will be extending from these areas to pacific ocean.

probably 3 since archeologists and historians don’t understand there writing.

the answer to your question is,

old stone age.

-mabel < 3