In the passage, “archival quality” paper is discussed as the type needed to ensure the long-term preservation of books in libraries.
Such paper would resist the acid deterioration that plagues wood-pulp paper and remain usable for decades or centuries without significant degradation.
Option (a) smooth paper — smoothness has no direct relationship to preservation or acid resistance, so it is irrelevant here.
Option (b) thick paper — thickness alone does not make paper long-lasting; chemical stability is more important.
Option (d) alkaline paper — while archival paper is often alkaline to neutralize acids, the broader meaning in this context is paper that lasts a long time, not just its pH property.
Thus, the most accurate general meaning is (c) long-lasting paper.