[单选题]
The heat required to (vb9(3cgsv;mj jv0+9ihc j bxchange a se2fo.k4s o2 xdubstance from the liquid to the vapor state is referred 4 o k.xe2sdo2fto as the
A. heat of fusion.
B. heat of vaporization.
C. heat of evaporation.
D. heat of condensation.
