Which letter corresponds to the month of October?

The month of October is the tenth month of the year in the Gregorian calendar, which is the calendar system used by most of the world today. In this context, identifying October among the choices provided is straightforward because it directly corresponds with the name "October."

Each of the other choices represents different months. November, for instance, comes after October, while June and December are farther away in different seasons (June being a summer month in the Northern Hemisphere and December being a winter month). Therefore, when asked for the letter corresponding to the month of October, it is clear that the correct answer is the one that explicitly names the month itself.