Analysis of test questions: This topic mainly examines the ancient political system of China. According to the meaning of the material, the vassal is the barrier of the country, indicating the purpose of the enfeoffment system; Han nationality is the pillar of the country and the main body of enfeoffment. Therefore, B and C are one of the specific contents of the enfeoffment system, which embodies the national management mode. A material will not reflect. So you should choose d.