Author(Writer):- Rudra Venkateshwarlu, MA. English, Spoken English Researcher since 7 years, Founder of Spoken English Hub, Nalgonda. Competitive English Trainer

Is what happened question or answer?

What happened    this is not question
What happened    this is answer

How means

What (question word). 
What happened  (question word sentence).

 Question word sentences are two types

1. Question word answer
2. Question word question


1.  question word answer

What happened
  QW         V2 

Where you are going
  QW       S     HV   V4

2.  question word question

What did happen?
QW     HV     V1

Where are you going?
QW       HV   S      V4

If helping verb is after Question Word means that is question.

 If subject or verb is after Question Word means that is answer.

Question :

What did happen?
QW      HV     V1

Answer :

What happened
 QW          V2 

English people are teaching wrongly. They did not know about language and meanings of the sentences.