Which of the following sentences is an example of an incorrect punctuation?

The sentence "Lets eat Grandma!" is an example of incorrect punctuation primarily because it omits the necessary apostrophe in "Let's." The apostrophe indicates a contraction for "let us," which clarifies that the speaker is inviting Grandma to join them for a meal. Without the apostrophe, the sentence humorously and alarmingly suggests that Grandma is the meal, which leads to a confusing and unintended meaning. In contrast, the other sentences correctly use punctuation, such as commas and quotation marks, to convey clear intentions and meanings in their contexts.