Final answer:
The correct answer is b. Starbucks. The word Starbucks is a proper name, so the possessive form should be Starbucks's.
Step-by-step explanation:
The correct answer is b. Starbucks.
When a noun ends in -s, such as Starbucks, the possessive form is made by adding an apostrophe after the -s, without adding another -s. So, it should be written as Starbucks'. However, when the -s at the end of a noun is part of a proper name, like Starbucks, the possessive form is made by adding an apostrophe and another -s. Therefore, in this case, we would write Starbucks's.
In this question, the word Starbucks is a proper name, so the possessive form should be Starbucks's.