if thegovernment launches campaigns to convey the message that asedentary job can affect health adversely and reduce life expectancy.
请问，这是什么句子， 为何用that， that前后都是完整句子，为何不需要介词➕which
这是that引导的同位语从句，对名词message作讲解说明。that为连词，不作成分。
if thegovernment launches campaigns to convey the message that asedentary job can affect health adversely and reduce life expectancy.
请问，这是什么句子， 为何用that， that前后都是完整句子，为何不需要介词➕which
这是that引导的同位语从句，对名词message作讲解说明。that为连词，不作成分。