[单选题]Choose the closest paraphrased version after the following sentence or the italicized part.Sometimes I think how grateful I would be today if I had learned more back then about what really matters.（ ） A I would be happy now if I had learned more about great historic events. B I would be satisfied today if I had learned more about things really important.  C Since I have learned how to deal with difficulties, I feel content with my education. D Since I have learned more than other students, I feel thankful to my school teachers.