Which of the below is true about brazil's araucaria trees?
a. they are one of the dominant trees in the brazilian amazon
b. they were once brazil's leading export, but are now almost completely gone
c. they have made a tremendous recovery due to government conservation efforts, and are now one of the big conservation success stories in south america
d. they are still very common, but are threatened with increasing harvesting for timber

d.They are still very common ,but threatened with increasing harvesting for timber.

Explanation:

Brazil's Araucaria trees:

   These trees are very soft and can be cut so easily.Brazilian pines is also know as Araucaria tree.

Before 1950's or 60's the number of trees were more but now due to harvesting the number of trees become less.The these trees are used for timber and for glue also.

In the present time the availability of these trees threatened with increasing harvesting for timber.

So the our option d is correct.