Which sentence shows correct punctuation of an introductory structure?

When I ran across the tile I lost my balance and slipped.
If I had stayed late on Friday, I could have caught up on my work.
Well I delivered the memo to Mr. Jenkins last week.
Miriam ran the copies, and then moved the files to the break room.

is it A?

No.

Please check your book to learn about introductory phrases and clauses.

is it d maybe i think either that or c i don't think it could be b

What on earth have you learned about introductory phrases and clauses?

This site will help you.

http://grammar.ccc.commnet.edu/grammar/commas_intro.htm

I think the Answer is B. Ms. Sue is that correct?

The sentence that shows correct punctuation of an introductory structure is:

"When I ran across the tile, I lost my balance and slipped."

Explanation:
An introductory structure is a phrase or clause that provides additional information at the beginning of a sentence. It is typically followed by a comma to separate it from the rest of the sentence. In this case, the introductory structure is "When I ran across the tile," which provides context for what happened next.