Question

according to the text, if humanity cannot be divided into a series of genetically distinct units, then
o the concept of race is biologically meaningless.
o human races are based on very specific genetic variations.
o microraces are the only biological possibility.
o the concept of race must be revised.

Explanation:

If humanity cannot be divided into genetically - distinct units, then the basis for differentiating races on a genetic level is absent. So, the concept of race loses its biological significance.

Answer:

the concept of race is biologically meaningless.