The Increased Production of Lamps Comes at Constant Opportunity Costs

The increased production of lamps comes at constant opportunity costs in terms of bookshelves.This means

A) that it takes more resources to produce a lamp than a bookshelf.
B) that it takes fewer resources to produce a lamp than a bookshelf.
C) that for every lamp produced, a constant number of bookshelves is forfeited.
D) that for every lamp produced, a different number of bookshelves is forfeited.