Teacher: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.
Teacher: Now, understand the problem? Solve this instance: Carl Sagan:  There are some hundred billion galaxies , each with , on the average , a hundred billion stars , 1011 x 1011 = 1022 , _ ten _ billion trillion . In the face of such overpowering numbers , what is the likelihood that only one ordinary star , the Sun , is accompanied by an inhabited planet ? Why should we , tucked away in some forgotten corner of the Cosmos , be so fortunate ? To me , it seems far more likely that the universe is brimming over with life . But we humans do not yet know . We are just beginning our explorations . From eight billion light - years away we are hard pressed to find even the cluster in which our Milky Way Galaxy is embedded , much less the Sun or the Earth . The only planet we are sure is inhabited is a tiny speck of rock and metal , shining feebly by reflected sunlight , and at this distance utterly lost .
Student:
REFERENCE stars