Which of the following islands did Columbus not name?

The answer is identified as Sandy Cay because this island was not named by Christopher Columbus during his voyages. Columbus is often credited with naming many islands in the Caribbean during his explorations, but he did not reference Sandy Cay, which is a lesser-known isle compared to the others mentioned.

In contrast, the islands of Cayman Brac and Little Cayman were certainly named in association with the Cayman Islands that Columbus encountered and referred to during his travels in 1503. Additionally, Los Tortugas, which translates to "The Turtles," was a name given by Columbus to what is now known as the Dry Tortugas, highlighting that it was indeed named during his expeditions. Sandy Cay, however, lacks such documented association with Columbus, making it the correct choice in this context.