By the early twentieth century, some anthropologists and biologists concluded that the concept of "race" was

a. justified by the increasingly scientific biological research on human beings
b. a cultural label invented by human beings to sort people into groups
c. a political liability, although the evidence was increasingly strong in its favor
d. a label that recognized important intellectual and biological differences among groups

b. a cultural label invented by human beings to sort people into groups

Explanation:

The concept of 'race' has been around for hundreds of years. However, as we evolve, our definition of race has changed and evolved as well. In general terms, race is defined as a grouping of individuals that are separated in regard to their cultural and physical features.

By the early twentieth century, researchers -anthropologists and biologists- proposed that race was actually a concept invented by humans or, in other words, a social construct with the purpose of separating people into groups based mainly in their physical similarities or differences.

according to classical republican political theory, which democratic republics would function best?

a.   small republics, with people who had similar interests

b.   large republics, with people who had competing interests

c.   republics made up entirely of landowners

d.   republics made up entirely of servants