Total stocks of most minerals in the earths crust are still large in relation to the current rates of use, and a high proportion of the minerals that are consumed in the production process could, in principle, be recycled. The technological and financial constraints on recycling such concentrations of minerals are considerable, however, and there is no guarantee that these constraints could be overcome. Substitution of abundant for scarce resources would avoid the problem, but such substitution is not always technologically feasible.

Question: Most of the minerals consumed in the production process can be economically recycled.
Options:
A. true, B. false, C. uncertain
Answer: "C"