A.) Which of the following sentences requires semicolons instead of commas?

B. On our summer road trip, we will travel by car, train, and bus to three different states.

C. This summer, we are going on a road trip to Philadelphia, Pennsylvania, Baltimore, Maryland, and Rehoboth Beach, Delaware.

D.) On our summer road trip, we will travel to Pennsylvania, Maryland, and Delaware.

This summer, we are going on a road trip to the cities of Philadelphia, Baltimore, and Rehoboth Beach.

C. This summer, we are going on a road trip to Philadelphia, Pennsylvania, Baltimore, Maryland, and Rehoboth Beach, Delaware.

The sentence that requires semicolons instead of commas is:

C. This summer, we are going on a road trip to Philadelphia, Pennsylvania; Baltimore, Maryland; and Rehoboth Beach, Delaware.

To determine which sentence requires semicolons instead of commas, we need to identify situations where semicolons are necessary. Semicolons are commonly used to separate independent clauses in a sentence or to separate items in a list when the items themselves contain commas.

Let's analyze each sentence:

A. "On our summer road trip, we will travel by car, train, and bus to three different states." - This sentence uses commas correctly because it is a simple list of items. No semicolons are required.

B. "This summer, we are going on a road trip to Philadelphia, Pennsylvania, Baltimore, Maryland, and Rehoboth Beach, Delaware." - This sentence contains a list of cities separated by commas. However, the cities themselves already contain commas (example: Philadelphia, Pennsylvania). In this case, semicolons should be used to avoid confusion. The correct sentence should be: "This summer, we are going on a road trip to Philadelphia, Pennsylvania; Baltimore, Maryland; and Rehoboth Beach, Delaware."

C. "On our summer road trip, we will travel to Pennsylvania, Maryland, and Delaware. This summer, we are going on a road trip to the cities of Philadelphia, Baltimore, and Rehoboth Beach." - Both sentences are grammatically correct and do not require semicolons. They consist of independent clauses that can stand alone as separate sentences.

Therefore, the sentence that requires semicolons is option B: "This summer, we are going on a road trip to Philadelphia, Pennsylvania, Baltimore, Maryland, and Rehoboth Beach, Delaware."