The Roman engineering achievement that made large public structures possible was A.) the development of concrete.

B.) the development of organized labor.

C.) the development of measuring devices.

D.) the development of advanced math concepts.

Opposition to the nra came to a head in 1935, when the conservative supreme court declared the agency unconstitutional, claiming the nra gave the executive branch regulatory powers that belonged exclusively to congress. this decision began a series of court decisions that overturned key elements of the new deal.