Most stars spend the majority of their lifetimes as which type of star?
a. giant
b. dwarf
c. protostar
d. main sequence user: a star's spectral class is related to which of these characteristics? select all that apply.
a. mass
b. radius
c. chemistry
d. temperature
e. distance to the center of its galaxy

Which of the following is part of the explanation or description of electromagnetic waves? (select all that apply) a. electrically charged molecules in a medium transfer their energy to nearby electrically charged molecules. b. a changing electric field causes a changing magnetic field. c. magnetic molecules in a medium transfer their energy to nearby magnetic molecules. d. a changing magnetic field causes a changing electric field.