Q: In this task, you will use your knowledge about language (and common sense) to determine what element the marked number refers to. The numbers are marked with two underlines around them, like: _ number _. There are several possible answers, you'll need to choose the proper one. Carefully read the given text, pay special attention to the marked number, think about what (unwritten) information the marked number holds inside, choose the most adequate word(s) from the optional answers. If none of them seems right to you, there's also an option for other. If your answer is "REFERENCE", also write the reference entity, otherwise write the implicit option name. Options to choose from are:
REFERENCE: Some object which is being mentioned in the text before or after the target number. The reference answer has a higher priority than any other. If both Reference and another answer are possible, prioritize the Reference.
YEAR: Describing a calendric year
AGE: Describing someone's age
CURRENCY: Reference to some monetary value e.g dollar, euro etc.
PEOPLE: Describing a single/plural persons
TIME: Describing a time of the day. Usually you can add the word o'clock after those numbers.
OTHER: Some other option, which isn't listed here.
Sheldon:  Do you want to hear an interesting thing about stairs ?
Leonard: Not really .
Sheldon: If the height of a single step is off by as little as two millimeters , most people will trip .
Leonard: I do n't care . Two milli - that does n't seem right .
Sheldon: It 's true - I did a series of experiments when I was _ twelve _ . My father broke his clavicle .
Leonard: Is that why they sent you to boarding school ?
Sheldon: No - that was the result of my work with lasers .
A:
AGE