Analysis of test questions: the materials only involve patent issues, which does not mean that there is a perfect economic and legal system, so A is wrong. According to the fact that the longest term of a material patent is five years, it is not aimed at official enterprise, so C is wrong and D is completely absolute. The materials reflect that the longest patent period is five years, and the application for 30 years is rejected, which is conducive to preventing monopoly, so B is selected.