d有歧义, it (knowledge) informed his literary style as much as the content of his fiction.
究竟是knowledge informed his literary style as much as knowledge informed the content of his fiction.
还是knowledge informed his literary style as much as informed the content of his fiction informed his literary style.
把"for costumers..calls."提取出来放在外面,会让整个句子看起来句意更紧凑更便于理解。把主语和谓语动词离开太远容易让读者误解。在不改变句意前提下优选A