[Grammar] But it seems that you don't want to warn him, I am wondering if there is some reason?

[kadioguy]

a. I know that everyone should follow this rule. However, I am afraid that Tom failed do so. But it seems that you don't want to warn him, I am wondering if there is some reason?

b. I know that everyone should follow this rule. However, I am afraid that Tom failed do so. But it seems that you don't want to warn him; I am wondering if there is some reason?

c. I know that everyone should follow this rule. However, I am afraid that Tom failed do so. But it seems that you don't want to warn him; I am wondering if there is some reason.
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Which one is grammatical? Or all of them are acceptable?

 

[AussieLexie]

I think C is the best of your three options. However, I would suggest the following:
I know everyone should follow this rule. I am afraid Tom failed do so, but it seems you don't want to warn him. I am wondering if there is a reason for this.
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I’ve removed ‘that’ x3 and tidied it up a little. You could use a question mark at the end if you wanted to soften it.

 

[kadioguy]

I am afraid that Tom failed do so.

Sorry, there is a typo. I think it should be I am afraid that Tom failed to do so.

You could use a question mark at the end if you wanted to soften it.

This helps a lot.

 

[kadioguy]

You could use a question mark at the end if you wanted to soften it.

If I want to say next time when this may happen, can I say the following?

You can use a question mark at the end if you want to soften it next time.

(update)
No one replied it so I have separated this topic into:

https://www.usingenglish.com/forum/...you-wanted-to-soften-it?p=1371223#post1371223