宾语从句的引导词本身有含义么?例如：The foreign ministry in Beijing urged the US to rectify what it described as America's mistake in bringing the charges.中国外交部敦促美国对指控加以修正,称美国在指控中犯下了错误.

这个要视情况而定的.引导词分为四种,分别是：
由从属连词that引导的宾语从句
由从属连词 whether,if 引导的宾语从句
由连接代词 Who,whom,whose,which,what引导的宾语从句
由连接副词 where,how,why,when引导的宾语从句
由从属连词that引导的宾语从句
that 在句中无词汇意义,在从句中不能充当成分,在口语当中往往省略
如：I hear (that) he will be back in an hour
由从属连词whether,if 引导的宾语从句
if/ whether “是否”,说明对陈述的事物不明确或不清楚.常用在ask,wonder,can(could) you tell me 等后.
如：I want to know if (whether) he will go tothe park with us
只能用whether 不能用if
在介词后面
如：I’m thinking of whether we should go fishing.
在动词不定式前：
They asked me whether to go skating
当与or not连用,或提出两种选择时
Mary asked whether I was doing my homework ornot.
宾语从句提前时：
Whether this is true or not,I can’t say
由连接代词 Who,whom,whose,which,what 和连接副词 where,how,why,when引导的宾从(代词或副词连接主句和从句,并在从句中担任句子成分,具有一定的意义,不可省略)
He asked who could answer the question
Please tell me where he is
Could you tell me why the train is late