Answer:
In the blink of an eye, the kids were ready to go to the movies.
Without a doubt, green is my favorite color.
Fortunately, the sleeping baby did not stir when the doorbell rang.
Believe it or not, the criminal was able to rob the same bank three times.
Explanation:
In all of these examples, there should be put a comma after an introductory phrase or word.
In the first sentence, the comma is put to separate the situation in which kids are going to the movies from the introductory phrase which can be left out here.
In the second sentence, a comma separates the introductory phrase, and also, can be left out here.
In the third sentence, a comma comes after an introductory word that is an adverb, fortunately.
In the fourth sentence, a comma is used to show important information.
