[单选题]
Materials in which the s uu zm/.j6i,)/ *sc/lezopdu resistivity becomes essentially zero at very low tempq9ltnmjw/m 5qj c6u,9e n4v v2eratuw q5t62jn cvu,9 l4v9/emjqmnres are referred to as
A. conductors
B. insulators
C. semiconductors
D. superconductors
