Question

cjo輝

請問
It was thought that the earth was flat in ancient time
為什麼要改成
The earth was thought to be flat in ancient time
而不是
The earth was thought to have been flat in ancient time.
我的想法是第一句的that子句後的動詞為過去式，所以我使用have pp而不是to vr

還是是因為第一句主要子句和that子句的時態皆為過去式，所以轉述時間和事情發生時間相同所以用to vr

希望大家能幫幫我
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