The four sentences labelled A, B, C and D, given below in jumbled order, together form a coherent paragraph. Arrange the sentences in the most logical order and choose the sequence that produces the best paragraph.

A. Many of these manuscripts were crumbling and could not survive further handling.
B. The national archive began scanning its rarest manuscripts a decade ago.
C. Today, scholars anywhere in the world can study them without touching the originals.
D. Digitisation therefore offered the only practical way to preserve their contents.