单选题 .  ①The first printers in Europe modeled their books very closely on handwritten manuscripts, leading to an easy acceptance of print among readers but to significant missteps in trying to apply technology. ②The attempt to replicate manuscripts' appearance encouraged experiments in two- or three-color printing. ③This was intricate and expensive work, and many printers found it preferable to pay expert calligraphers to manually adorn unbound sheets with additional colors. ④Illuminated headings and decoration familiar from the manuscript age had helped lead readers through the text. ⑤To achieve similar effects, printers began to experiment with new arrangements of type, using large fonts for headings and substituting decorative woodcuts for hand-executed initial letters. ⑥Ultimately, readers came to accept books printed in just one color.27.  The author suggests that readers of the earliest books printed in Europe ______