Which of the following sentences is punctuated incorrectly?

A.
Oh! I didn’t know the party was tonight.

B.
Shreya, the birthday girl, would understand if I was late.

C.
In the afternoon, I stopped to pick something up from the store.

D.
After you left I picked up the present a stuffed animal.

And your answer is?

Btw -- B has a grammatical error. Because it's in the subjunctive mood, the verb should be "were." Please remind your teacher of this.

https://en.oxforddictionaries.com/grammar/when-to-use-the-subjunctive

To identify the sentence that is punctuated incorrectly, we need to review the punctuation of each sentence. Let's go through them one by one:

A. "Oh! I didn't know the party was tonight."
This sentence appears to be punctuated correctly. The exclamation mark is appropriate because "Oh!" expresses surprise.

B. "Shreya, the birthday girl, would understand if I was late."
This sentence also seems to be correctly punctuated. The comma is used to set off the appositive phrase "the birthday girl" that provides additional information about Shreya.

C. "In the afternoon, I stopped to pick something up from the store."
This sentence appears to be punctuated correctly. The comma is used to set off the introductory phrase "In the afternoon" from the main clause.

D. "After you left I picked up the present a stuffed animal."
Upon reviewing this sentence, we can see that there is a mistake in punctuation. The correct punctuation should have a comma after "present" to separate it from the phrase "a stuffed animal." The corrected version would be: "After you left, I picked up the present, a stuffed animal."

Therefore, the sentence that is punctuated incorrectly is D. "After you left I picked up the present a stuffed animal."