What he really means【主语（What引导的主语从句）】
is 【系动词】
that he disagrees with us【表语（that引导的表语从句）】
句子为 主系表 结构
主语从句分析：What he really means
从句充当主语,由连接词what引导,并且在从句中充当【mean的宾语】
即为：he really means What
表语从句分析：that he disagrees with us
从句充当表语,由从属连词that引导,that无实际意义,在从句中不充当任何,仅是连接作用
表语从句句型：be+表语从句
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