A president's legislative initiatives are significantly more successful when the President is a member of the same party as Congress.
This is due to a system that rewards legislative accomplishment and legislative obstruction.
If the President is a member of a different party from Congress, then there is a good chance that the members of Congress will be unwilling, in the current environment, to "reach" across the aisle and work with the President on legislation.
Answer:
History
Explanation:
The history of the students in relation to their mathematical skills is a potential threat to validity of the experiment.
I think that a good answer here is "selling": a market economy is also said to be determined by supply and demand, which means that the people who produce and sell make decisions about what is available (supply) and this interacts with the decisions of the buyers (demand).
