. Identify which one of the following sentences is missing punctuation. Please correct the error and explain why the correction is necessary.

a. I woke up when the book slipped from my lap and landed on my foot.
b. After the book slid from my lap and landed on my foot I realized that I had fallen asleep.

We'll be glad to check your answer.

the first one doesn't need any puncuation.

After the book slid from my lap and landed on my foot; I realized that I had fallen asleep.

You're right about the first sentence.

I'm not sure whether you have a comma or semicolon after foot. You need a comma there.

why do i need to add a comma there

You need a comma to separate the introductory clause from the independent clause.

http://owl.english.purdue.edu/owl/resource/607/02/

The sentence missing punctuation is sentence b: "After the book slid from my lap and landed on my foot I realized that I had fallen asleep." The correction necessary is to add a comma after the phrase "on my foot" to make the sentence grammatically correct.

The corrected sentence would be: "After the book slid from my lap and landed on my foot, I realized that I had fallen asleep."

The correction is necessary because the phrase "After the book slid from my lap and landed on my foot" is an introductory phrase. Introducing a sentence with a phrase requires a comma after the phrase to separate it from the main clause. Adding the comma clarifies the sentence structure and makes it easier for readers to understand the intended meaning.