文法問題，infer rules underlying the speech 的 ing - 英檢

眾文TOEFL iBT 托福分類字彙，第21篇，Language Acquisition by Children

第二段第三句， 原句很長，所以我只取重點

..., and the main problem to which it has addressed itself has been how it is possible for young children to infer the grammatical rules underlying the speech they hear and then ....



想請問一下，為什麼那個underlying會有ing呢？

infer的用法有
1. infer sth. from sth.
2. infer that

看起來應該跟infer沒關係

難道是因為underlying前面有個省略的which is嗎？

謝謝各位

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