Why do historians divide history into eras?

Click on  the link  to view information gathered by the organization keep america beautiful. read "the costs of american littering" to find three negative effects of litter in local communities.  based on your research, what are the negative effects of litter in local communities? check all that apply.litter cleanup is very expensive.litter has decreased since 1969.litter is a constant community problem.litter causes property in the community to be less valuable.litter contaminates water and has other environmental consequences.

According to the federal regulations, which of the following studies meets the definition of research with human subjects? a researcher conducts a comparison of the comments made in a publicly available blog and the blogger's comments on a similar topic in a weekly magazine. undergraduate students in a field methods class are assigned a research question and asked to interview another classmate, to be followed by a class discussion on interview techniques. a cognitive psychologist enrolls undergraduate students for a computer-based study about the effect of mood on problem-solving behaviors. a researcher sets up a meeting with the superintendent of a large and diverse public school system to get data about the ethnic composition of the school system and the number of students receiving free lunches.

What are the roles of the fcc in the us? check all that apply. regulating the country’s communications infrastructure ensuring communication technology is compatible with existing technol