You're welcome. :-D
Try,
Do you know how thunderstorms are formed? :up:
Do you know how a thunderstorm is formed? :up:
Can you tell me who that girl is? :up:
To form an object (e.g., that girl is) take the statement and move who to the front, like this,
Statement: That girl is who?
Object: . . . who that girl is?
Example: Can you tell me who that girl is?
That girl is the subject, is is the verb and who is the object, or in this case, since is is a form of the verb BE, who functions as a predicate nominal, technically speaking.
Other examples,
She is who?
I wonder who she is.
The next example does not require WH-movement. 'Who' is the subject,
John is reading this.
Who is reading this?
I wonder who is reading this? (grammatical) :up:
The example below requires WH-movement because what functions as an object in that sentence. When the WH-word functions as a subject movement isn't required:
She saw what?
I wonder what she saw?
I wonder what she did see? (did is added for emphasis)
She sees what?
I wonder what she sees?
I wonder what she does see? (does is added for emphasis)
Thunderstorms are made how?
Can you tell me how thunderstorms are made?
Hope that helps out some. :up: