Test analysis: This question mainly examines students' ability to mobilize and use knowledge. According to the knowledge learned, "letting a hundred flowers blossom and a hundred schools of thought contend" is the policy of letting a hundred flowers blossom and a hundred schools of thought contend on artistic issues, and it is also the guiding principle for the prosperity and development of socialist science and culture determined by the CPC Central Committee in 1956. The proposal of "long-term coexistence and mutual supervision" correctly solved and handled the relationship between China and the democratic parties, greatly promoted the expansion of socialist democracy and the unity of the people's democratic United front, and also provided a solid foundation for the continued development of the multi-party cooperation system in China. Thereby excluding item c; B is the function and influence of the policy of "letting a hundred flowers blossom", which has nothing to do with "long-term coexistence and mutual supervision"; The adjustment of China's national economy was carried out in the early 1960 s, and D's statement has nothing to do with this issue, which is wrong. So the answer to this question is a.