Please help I’m begging

How did the technology of the late 1800s affect the growth of cities? select one: a. cities were able to expand outward because of additions to railroads. b. electric streetcars enabled the wealthy city dwellers to move to the first suburbs. c. advances in steel and metal technology allowed for the development of the skyscraper, which allowed cities to grow upwards. d. all of these are correct.

Who did the first work in creating vaccines

Which agency is under the authority of the department of labor? sec osha epa fda