1. The core test sites involve complex concepts or theories, which are abstract and require high thinking ability and logical reasoning ability to understand. This brings difficulties to students, and requires in-depth study and thinking to fully understand.

2. The core test center requires students to comprehensively use the knowledge and skills of different disciplines to solve problems. This requires students to have the ability of interdisciplinary thinking and comprehensive analysis, and also requires in-depth understanding and mastery of the knowledge of different disciplines. This comprehensive requirement makes the core test center more difficult.