Read the following context and choose the best option to answer the question.
Context: Roland took the kids shopping for school supplies . He came back miserable that he had spent $ 100 . The kids wanted these fancy binders , and mechanical pencils , and Gary wanted a little white board to write his assignments on . Then he just bought erasers and notebooks and stuff .
Question: Why was Roland so upset ?
Options: 
A. Because the children had been hard to control while shopping
B. Because while they were shopping , the kids had been unruly
C. Because the kids had misbehaved in the store and knocked things over
D. Because he had n't anticipated the extent of his kid 's demands


D