A "This one" (line 54) refers to "document scanning service" (line 52).
B "It's" (line 43) refers to "compact discs" (lines 42-43).
C "Their" (line 35) refers to "applications" (line 33).
D "Each one" (lines 25-26) refers to "document" (line 24).
E "Others" (line 19) refers to "options" (line 17).