Which renewable source of energy should the united states focus its research and development efforts to make this source of energy our country’s main energy source by the year 2050? why?

The areas with the highest population density in europe are most likely to be

Which is the most accurate description of the executive office of the president? groups of advisers who the chief of staff groups of advisers who the president groups of advisers who oversee national security groups of advisers who oversee the economy

The authors of the paper "fudging the numbers: distributing chocolate influences student evaluations of an undergraduate course"† carried out a study to see if events unrelated to an undergraduate course could affect student evaluations. students enrolled in statistics courses taught by the same instructor participated in the study. all students attended the same lectures and one of six discussion sections that met once a week. at the end of the course, the researchers chose three of the discussion sections to be the "chocolate group." students in these three sections were offered chocolate prior to having them fill out course evaluations. students in the other three sections were not offered chocolate. the researchers concluded that "overall, students offered chocolate gave more positive evaluations than students not offered chocolate." indicate whether the study is an observational study or an experiment. give a brief explanation for your choice.