The difference in English language between...? please help?

Question

Hello I'm quite confused

would like to know what's the difference between :

1-the subject questions in the past tense ( Tom ate the apple- Who ate the apple) ->the rule of keeping the statement order.

http://www.english-zone.com/grammar/questions4.html

and

2- the normal question formation

Question word+ Aux.v+ S.+ V?

why the senetce above shouldn't be this way:

who did eat ?

if they are two separate rules , how could I diffrenciate btw them

plz help me I need your help

thank you

FIDO

Answer 1

when you ask using who, you dont follow the main rule

just say (who ate the apple?)

this is English don't ask why about garammer,just learn it

Answer 2

The trick is whether the question is about the subject or about something else.  If you start with "Tom ate the apple," and you want the answer to be "Tom," you will ask "Who ate the apple?"  You are asking about the subject of the sentence.  If you want the answer to be "the apple," you will ask "What did Tom eat?" (Question word, auxiliary, subject, verb, just as your rule states) but you are asking about the object.  In any question where the answer is not the subject of the sentence, a form of "do" is needed for action verbs.  (Reasons: "Why DID Max eat the apple?" Times: "When DOES the train arrive?" Places: "Where DO they keep the keys?" etc.)  When the answer is the subject, no form of "do" is needed.  (What fell off the shelf?  Answer:  The book fell off the shelf.  "The book" is the subject.  "Who believes those lies?"  Answer: Calvin believes those lies.  "Calvin" is the subject.)  If that does not answer the question you are confused about, please feel free to drop me a note.