Identify the sentence that has an appropriate shift in verb tenses. A. She spent most of her time having fun with friends and her grades suffered, so she learned to manage her time more carefully. B. She will spend most of her time having fun with friends and her grades will suffer, so she will learn to manage her time more carefully. C. She had been spending most of her time having fun with friends and her grades had suffered, so she had learned to manage her time more carefully. D. She spent most of her time having fun with friends and her grades suffered, so now she manages her time more carefully.