What distinction can be made between the preoperational stage of development and the concrete operational stage?

Mr. mann's science students were experimenting with speed. they set up a 1 meter (100 cm) track. the students used balls instead of cars. the balls were different sizes and made of different materials. four at a time, students rolled balls around the track to see which had the fastest and slowest speeds. some of their data are shown in the table. which ball will take the longest to complete one lap around the track?

All of the following statements point out negative aspects of the gilded age except: a. politicians gave government jobs to political supporters. b. political bosses cheated large cities out of millions of dollars. c. industrialists bribed members of congress to ensure favorable votes. d. in 1903, wisconsin became the first state to hold primary elections.

Which statement about spreading knowledge of diseases and health around the world is correct?