11) Choose the best answer. Which sentence has incorrect comma usage? Unless you plan to buy the item, please do not touch it. Gretel always gets nervous when she speaks in front of the class. I came as soon as I heard the news, which I was very happy about. You can come over for dinner whenever you want.

The question asks us to identify the sentence with incorrect comma usage. Let's analyze each sentence:<br /><br />1. "Unless you plan to buy the item, please do not touch it." - This sentence correctly uses a comma after the introductory clause "Unless you plan to buy the item."<br /><br />2. "Gretel always gets nervous when she speaks in front of the class." - This sentence does not contain a comma, and it is not necessary as there is no introductory clause, no list, or no independent clause that needs to be separated.<br /><br />3. "I came as soon as I heard the news, which I was very happy about." - This sentence incorrectly uses a comma to separate the independent clause "I came as soon as I heard the news" from the dependent clause "which I was very happy about." The dependent clause is providing additional information about the news, and it should not be separated from the independent clause by a comma.<br /><br />4. "You can come over for dinner whenever you want." - This sentence does not contain a comma, and it is not necessary as there is no introductory clause, no list, or no independent clause that needs to be separated.<br /><br />Therefore, the sentence with incorrect comma usage is the third one.