which is is which

Do you fail to tell which is the subject of this sentence?

Do you fail to tell which the subject of this sentence is?

Basic English grammar

Where is John?(a question)

Do you know xxx?(a question)

Do you know where is John? Wrong! 'Do you know...' is the beginning of a question, so you are not supposed to throw in 'where is John'.

Do you know where John is? Correct! 'where John is' is not a question.

It looks like the second question is correct, but it isn't.

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The writer tried to talk about the past.( I saw his work, but I cannot post the link here for fear that someone will erase this thread.)

He shouldn't have used the present tense.

1. Do you fail = the simple present tense
It means this person always fails to do something.
2. the subject of THIS sentence( Since the simple present tense is used, it is
confusing to talk about THIS sentence.)

If that bloke always fails to tell what the subject is in this sentence all the time, we may say it. ( Perhaps, that guy is a retard?)

e.g. Do you always fail to construct simple English sentences?( No 'these')

The correct tense should be the simple past tense in this case.
e.g. Did you fail to tell which the subject of the sentence WAS?

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If you want to say someone always fails to do something, you may use the present tense.

e.g. Do you fail to tell the subjects of sentences? (still unnatural and Chinglish)

A better version is:

Do you always have problems telling people what the subject is in a sentence?

or
Do you always have problems telling people what the subjects are in a sentence? (Some sentences have more than one subject.)

To conclude, the first question is grammatically wrong and the second one is Chinglish or Singlish to me.

Obviously, the writer could not tell the difference between ' the simple present tense' and ' the simple past tense'. He should also have had difficulty using 'articles'.

2014-06-25 11:25:28 補充：
Yahoo is acting up again!

He shouldn't have used the simple PAST tense.*****************

The second one is correct.

The reason is "Do you fail to tell" is followed by a noun phrase.

~ Do you fail to tell a story?
~ Do you fail to tell something secret?
~ Do you fail to tell this?

A similar example is:
"Do you know who I am?"