It consists of a more restrictive set of conditions to validate the KDC's certificate, predominantly it demands a KDC certification using an EKU of “KDC Authentication” (see possibility b. higher than). 雅思考试和四六级应试考试不同，主要是能力型考试，主要考察，解题+科目能力+词汇+语法+逻辑，所以四、