【单选题】Most of the pioneers of low-temperature physics expected gases to liquefy, but none of them predicted superconductivity. This phenomenon was discovered in 1911 by Onnes while he was studying frozen me...
A.
electrons circle rapidly around the atom
B.
the outermost electron move relatively freely around the atom
C.
the innermost electrons stick to the atom
D.
the outermost electrons are bound tightly to the inner ones