Which answer choice correctly describes how the US Constitution fixed a problem or problems of the Articles of Confederation? O A Under the Constitution, the people could directly elect their representatives in the US Senate.
OB. Under the Constitution, the state governments were granted more control over immigration and trade.
OC. Under the Constitution, the federal government had the power to enforce laws but was checked by Congress and the court syst
OD. Under the Constitution, political candidates must be a member of a political party so that they represent the interests of the
people.

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.