閱讀 - 英檢

各位好,

小弟在做閱讀測驗時, 對於下面句子的結構感到不解, 請各位高手幫忙分析一下:

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The frequency of advertisement is not always perceived by consumers to

indicate that manufacturers are highly confident about their product's

quality.

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"The frequency .... by consumers" 是一個完整句子,

為什麼後面可以直接接 "to indicate that ..."?

是因為省略 (which is) to indicate that... 嗎?

如果是的話, 那請問先行詞是甚麼呢?_?

謝謝
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