Ms Green Has Designed a Grading System Whereby Each Student

Ms. Green has designed a grading system whereby each student has a chance to earn an "A" in her class. Each exam, book report, and homework assignment is graded based on the how much total knowledge a student has mastered in that particular area. Ms. Green then just takes an average of all the smaller grades to assign overall grades. Ms. Green is using which of the following grading systems?

A) contract system
B) percentage grading system
C) summative system
D) total point grading system