To find the assumption made in drawing the passage conclusion, we have to find the answer choice that contains accurate and truthful information in order for the passage assumption to be valid.

We can say from the message portrayed in the passage that "the exports of United States wood pulp will rise considerably during this year due to the falling value of the US dollar."

Option A - Incorrect
This answer choice is incorrect because we cannot know from the passage if the production of paper products will increase during this year in Japan and Western Europe.

Option B - Correct
The fact that paper manufacturers in Japan and Western Europe will find it easier to capitalize on the cheap price in getting American wood pulp directly as compared to getting it from other sources this year validate the passage conclusion of considerably rise in exporting of American wood pulp to other nations due to the falling value of the dollar.

Option C - Incorrect
This assumption is irrelevant in drawing a conclusion from the passage.

Option D - Incorrect
This claim goes too far in its assumption. We are not concerned about the demand for paper products in Japan and Western Europe this year.

Option E - Incorrect
It's assumed from the passage ("...will rise considerably during this year") that wood pulp is readily available for export to other nations because the passage didn't discuss any stop in the production of wood pulp for export in the United States.

So, therefore, this answer choice's claim if true will contradict the passage stand on the predicted increase in exporting of wood pulp in the United States.