✨ ベストアンサー ✨
(1) → We (were) (made) (to) (write) an essay on environmental pollution.
※[be made](使役動詞makeの受動態) to ~ ~させられるb
(2) → She (has) never (been) (heard) (to) (speak) English.
※[be heard](知覚動詞hearの受動態) to ~ ~するのを聞かれる
(3) → The boy (is) (believed) (to) (be) a genius.
→ (It) (is) (believed) (that) the boy is a genius. <形式主語構文>
(4) → Rosa (is) (said) (to) (live) in Spain now.
→ (It) (is) (said) (that) Rosa lives in Spain now. <形式主語構文>
参考にしてください。