[单选题]
Materials in which the resken uevo*p x)mlp9e .s ft7 fvto-2,.1 q o-pwz 4ukm8xzr.86nistivity becomes essentially zero at very low temperatures are rq.w p6 u8z-4n8krmxzoeferred to as
A. conductors
B. insulators
C. semiconductors
D. superconductors
