Why Do Achievement Tests Need to Have Their "Stakes" Risen

Why do achievement tests need to have their "stakes" risen?

A) The higher stakes create a prospect of greater rewards, which causes students to increase their effort toward academic achievement.
B) Higher stakes will mean bigger rewards for teachers whose students score high on achievement tests.
C) Actually, requiring more courses in math and science is a more promising policy for increasing achievement.
D) Higher stakes achievement tests will require that students only work a limited number of hours per week.