Which letter does the Greek letter 'Ω' represent?

The Greek letter 'Ω' represents the letter Omega. Omega is the 24th and last letter of the Greek alphabet, and it is commonly used in various contexts beyond just the alphabet itself, including mathematics, physics, and engineering. For instance, in electrical engineering, Omega often symbolizes ohms, the unit of electrical resistance.

In contrast, the other letters mentioned in the choices represent different Greek characters. Alpha is the first letter of the Greek alphabet, Gamma is the third letter, and Delta is the fourth. Each of these letters has its own distinct meanings and uses, but they are not represented by the symbol 'Ω.' Thus, the selection of Omega as the representation of 'Ω' is accurate and aligns with the conventions of recognizing Greek letters.