[单选题]
Materials in which thtom: w: ww1.ziop3n 8cexxh ku48o1b0-k amff .j qmq 5-wb(ys3 electrons are bound very loosely to the nuclei and can move about freely 3m k5 mqsbx--k h0faw8uf1(4yxjq .b owithin the material are referred to as
A. insulators.
B. conductors.
C. semiconductors.
D. superconductors.
