人+used to Vr

[black17 (喔郎)]

剛剛看到一題
Mary’s reluctance to work as hard as she used to ______ the way she was treat
ed in terms of salary and promotion.

結果答案是resulted from 為什麼不是result from呢，前面的to應該不是介系詞吧？
求解 謝謝各位

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→ dunchee: Mary's reluctance(主詞) [to work as hard as she used
→ dunchee:                                      to] __動詞__
→ dunchee: 就算是 result 可以也得加上 s (第三人稱單數)
→ dunchee: resulted 是簡單過去式
→ dunchee: [to <work> as hard as she used to <work>] : 不定詞相
→ dunchee: 關用法。後頭的 <work>(動詞) 不用再加。to不是介詞
→ mohiwa: 同上,你把句子斷在used to,就會比較容易看懂了
推 linkodak: result from 是本句的重要動詞，前面都是主詞
推 linkodak: 主要