Star a is a main sequence star of spectral type f2 and star b is a white dwarf of spectral type b4.
which statement below is correct?
star b appears brighter than star a.
star a appears brighter than star b.
star b is hotter than star a.
star a is hotter than star b.
none of the above can be said about these two stars.

Star B is hotter than star A.

Explanation:

A main-sequence star of spectral type F2 has an average temperature of 6000K - 7500K.

A white dwarf B4, is essentially a dying star, and in its final stage of life, the star will start to cool down slowly, however, this process is terribly slow and during they lifetime, they have an average temperature of around 10.000 K - 30.000 K. Thus, Star B is much hotter than star A.

answer at the divergent plate boundary in the middle of the ocean;