Which best explains how the structure of the executive office of the president fulfill presidency's office's role? the office is led by the chief of staff, who serves as a key adviser to the president. the office has multiple levels of staff and advisers who the president in many areas. the office is led by the vice president, who serves as a key adviser to the president. the office has a single level of staff and advisers who the president in many areas.

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.