Answer is B

The manager at the office supply store believes that the new CLP-300 laserjet printer will be used more as a replacement for printers in small offices and libraries rather than for high quality and feature-packed machines in large company settings because its noise emission, only 43 decibels, is far less than most other laserjet printers, which make about 50 decibels of noise each.

(A) more as a replacement for printers in small offices and libraries rather than for high quality and feature-packed machines in large company settings because its noise emission, only 43 decibels, is far less than
(B) more as a replacement for printers in small offices and libraries than high quality and feature-packed machines in large company settings because it emits only 43 decibels of noise, far quieter than
(C) as a replacement for printers in small offices and libraries more than for high quality and feature-packed machines in large company settings because it emits only 43 decibels of noise, far less than
(D) as a replacement for printers in small offices and libraries more than high quality and feature-packed machines in large company settings because its noise emission of only 43 decibels is far quieter than it is for
(E) as a replacement more for printers in small offices and libraries rather than for high quality and feature-packed machines in large company settings because its noise emission, only 43 decibels, is far less than than it is for

Eliminated A & E: more...rather than (incorrect idiom);
D - 'it' referring to !!! donn know + Comparison error : its (laserjet printer's) noise emission of only 43 decibels is far quieter than it (laserjet printer !!! or noise emission) is for

C vs B : 'more' is changing position in B & C

in C - pallelism problem 'used as a replacement for printers....more than for high...machines' (here author intends to compare printers & machines and so...better would be to bring 'more' before 'for printers').

in B - 'used more as a replacement for printers....than high...machines' + quieter (better than less bcoz its related to sound pollution) - IMO