原句：A new survey shows that 54 percent of Americans do not take prescription medicines as instructed though they are important to their health.
在这句句子中,主句是：A new survey shows ,主语是a new survey
that引导的是宾语从句,指shows的内容.that 54 percent of Americans do not take prescription medicines as instructed though they are important to their health.是宾语从句,主语是54 percent of Americans .
在宾语从句中还有一个从句,由though引导,从句是they are important to their health.而这句从句主语是they,指代prescription medicines
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