Of the Thousands of Cases Submitted to the U

Of the thousands of cases submitted to the U.S. Supreme Court each year, why does the Court-aside from obvious workload considerations-hear only a small minority of them?

A) Many of the submitted cases are frivolous.
B) to show proper respect to the rulings made in the lower courts
C) to show proper respect to the other branches of government, and to fend off charges that the Court takes an activist role in policy making
D) Article III of the U.S. Constitution limits the number of cases that the Supreme Court can consider each year.
E) The Court is too divided to agree on cases.