Which advancement in technology has cut down on waste

The question above is incomplete. The options attached to the question are as follows:
 A) Milk cartons
B.) Computer monitors
C.) Disposable tapes
D.) E-mail

ANSWER
 The correct option is D.
   Before the advent of e-mail, huge amount of papers are used in the process of writing letters. The writing materials,the envelopes and the stamps are all made of paper and this led to a great waste as the papers have to be disposed after use.This is not the case with electronic mails. Electronic mails do not need paper at all and it has drastically reduce the amount of papers that is used in writing letters.