The expression the Dark Ages (lines 11 and 12)...

can be also spelled as the dark ages, without resulting in any change in meaning in this context.

alludes to a period in the tourist industry when business was rather slow and there was a general feeling of pessimism.

means any period, real or imaginary, of great personal sadness and frustration.

refers to human beings’ old age, when they are approaching their death.

describes a particular chronological age in history.