(accidentally put it as biology) How does the author distinguish between picture engraving and letter engraving in the “Tools of Engraving” section?

by highlighting the impressive style and artistry of picture engravers as opposed to the simplistic and minimalistic style of letter engravers

by detailing the complex tools used in picture engraving as opposed to the basic tools used in letter engraving

by stressing the short apprenticeship lengths required for letter engraving as opposed to the extensive apprenticeship lengths required for picture engraving

by describing the firm guidelines letter engravers follow as opposed to the more interpretative techniques picture engravers follow