Punctuation when using ' for example' [closed]

Which of the following punctuation is correct:

1) Ask questions, for example, "what is the author's purpose?"
2) Ask questions. For example, what is the author's purpose?
3) Ask questions. For example: 'What is the author's purpose?'

"Ask questions" and the rest can be seen grammatically either as two separate sentences (separated by either a sentence break or a semi-colon) or as a general command and a specific case (separated by a colon). Two colons in a single sentence isn't good, so if you use a colon here, don't use one after "for example".

Quotes aren't really necessary around the question, since it's clear that it's an example question to be asked and you're not actually asking it yourself.

Either a comma or a colon would be fine after "for example", but a colon is probably better.

So the best possibilities are:

Ask questions; for example: what is the author's purpose?
Ask questions. For example: what is the author's purpose?

The second of these is probably better, since a colon and semi-colon in the same sentence doesn't look good.