Statements:
1. Some papers are pens.
2. Angle is a paper.

Conclusions:
I. Angle is not a pen.
II. Angle is a pen.

Let us evaluate the connections between the classes:
1. "Some papers are pens" means the sets 'Papers' and 'Pens' overlap.
2. "Angle is a paper" means Angle belongs directly inside the set 'Papers'.

Since Angle is a paper, and only a part of papers are pens, Angle might fall inside the overlapping pen region or outside it.

* Conclusion I ($\text{Angle is not a pen}$) is possible but not certain.
* Conclusion II ($\text{Angle is a pen}$) is also possible but not certain.

Because these two statements are mutually contradictory and exhaustive over the state of Angle's relation to pens, they form a classic either-or complementary pair. Thus, either conclusion I or conclusion II must be true.