Today,when my English teacher helped me and my classmates to scan through the chapter one in the volume one of Harry Potter,she asked us to write a composition. However,the topic she wrote was a little odd to me.
Tell one thing that Ms.Dursley was afraid of the Potters.
To be honest,I knew what she wanted to say was 「tell one of the reasons Ms.Dursley was afraid of the Potters」. Thus,I really believed its structure had a grammatical error. And then,I told her that she should correct it to the sentence "tell one thing that Ms.Dursley was afraid of the Potters for ". Notwithstanding,she said she didn't understand why the sentence needed "for" at the end. So, isn't there the error in her sentence?Why or why not?
If it had errors,how to correct it in the best way?