Read this sentence from abraham lincoln's second inaugural address:
it may seem strange that any men should dare to ask a just god's assistance in wringing their bread from the sweat of others men's faces; but let us judge not that we be not judged.
to what does the phrase sweat of other men's faces refer? (4 points)

a. the moisture of exertion
b. the owners of plantations
c. the suggestion of work
d. the toil of slaves