D

Test question analysis: ① It does not meet the meaning of the question and the truth is not involved in the material. It is specific and conditional. ② It does not meet the meaning of the question, and the material does not involve the repetitive nature of understanding. ③ In line with the meaning of the question, it can be reflected in the material that "the more you know, the bigger the circle will be, and the more you don't know." ④ In line with the meaning of the question, it can be reflected in the material that "the more you know, the bigger the circle will be, and the more you don't know." Therefore, keep ③④ and choose D.

Comments: This type of test questions requires students to master the continuous pursuit of truth in practice. Truth is people's correct reflection of objective things and their laws. Truth is objective, concrete, and conditional. Understanding is repetitive, infinite, and rising. People's understanding advances in waves and spirals. Methodology: Keeping pace with the times, pioneering and innovating, understanding and developing the truth in practice, and testing and developing the truth in practice are our unremitting pursuit and eternal mission. This question is of moderate difficulty and tests students' ability to analyze based on book knowledge and combined with materials.