Martha, a Mother of a Fifth Grader, Was Praising Her

Martha, a mother of a fifth grader, was praising her son for his hard work and effort on his first test.She was pleased ______.

A) that he did so well
B) to know of Dweck's study that praising for hard work and effort caused fifth graders to choose the more difficult problem the next time
C) he studied hard for the test
D) his grades were improving