In which one of the following sentences is the apostrophe used correctly?
a. i put the letter back into it's file.
b. the train began it's journey across country.
c. the cat licked it's paws while the dog watched.
d. it's up to you to decide what to do.

1) is right

step-by-step explanation:

answer: on graphs, the open and closed circles, or vertical asymptotes drawn as dashed lines us identify discontinuities.

as before, graphs and tables allow us to estimate at best.

when working with formulas, getting zero in the denominator indicates a point of discontinuity.

when working with piecewise-defined functions, check for discontinuities at the transition points where one piece ends and the next begins.

step-by-step explanation: