Scientifically speaking, race and ethnic groups are (points : 1) similar in that both are culturally defined. similar in that both are biologically determined. fundamentally different in that ethnicity is based on biology while race is a purely cultural construct. fundamentally different in that membership in an ethnic group can be changed but membership in a race cannot

I would choose this option:  fundamentally different in that membership in an ethnic group can be changed but membership in a race cannot

but generally "race" is a very problematic concept. In any case: ethnic group is more connected to the culture (adopted children have the ethnicity of the culture of their parents if they identify with it, while they would not necessarily have their 'race")