A Food and Drug Administration rule implemented in December 2000 mandates that any new drug that they intend to be used both by adults and children must undergo pediatric study and that its manufacturers list children's doses on the label.
drug that they intend to be used both by adults and children must
drug whose intended use is for adults and children as well
drug intended for use by both adults and children
drug, if they intend that it be used by adults and also children, must
drug, if intended for use both by adults and children, must
A可以排除因为定语从句不缺成分,也就是多了一个they。
那B和C呢?感觉语意有一点差别
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