Hi, for a necessary assumption question, the right answer will be something the author must agree with if their argument is to make sense.
While the author certainly has to believe that there is an inverse relationship between tv and math ability, it does not have to be the case that there is a dividing line at one hour a day of tv. Maybe this inverse relationship only starts after a child watches two or more hours a day.
E does have to be true, if there is something else that causes the relative weakness of US math students, then the authors argument that it is TV is much weaker.
