The eighth month of the year is

The Gregorian calendar orders the twelve months in a fixed sequence: January, February, March, April, May, June, July, August, September, October, November, December. Each ordinal position, first through twelfth, belongs to exactly one month.

Counting to the eighth position in this sequence lands on August: July occupies the seventh position, and September comes after August in the ninth position. Since August itself is not among the options offered, none of the listed months can be the eighth month.

• July holds the seventh position, one before the eighth, so it cannot be the answer.

• September holds the ninth position, one after the eighth, so it cannot be the answer.

• October holds the tenth position, two after the eighth, so it cannot be the answer.

• Only one month can occupy a given ordinal position at a time, so the option claiming more than one month fits cannot hold.

Because the eighth month, August, is absent from the options and each offered month occupies a different position, the only option that fits the calendar's structure is the one indicating no listed month is correct.