that引导的内容做什么成分

题目

that引导的内容做什么成分
It appears ,the neuroscientist says,that exercise not only slows negative changes to the brain but also gives you some cognitive reserves,so that even if the plaques implicated in Alzheimer's disease do appear,they don't have the same impact that they would on a couch potato.
请问后面that they would 是定语从句吗?如果是,从句部分的主谓宾是什么呢

答案

是定语从句修饰 impactimpact that they would (have) on a couch potato.impact 是先行词,that 是引导词代替impact、在从句中作宾语,they 是从句主语,would (have) 是从句动词短语：have ...impact on.."在...上起...