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Explanation:
The parallactic second represents distance or length and therefore, does not have a unit of time. Hence, the correct answer is option (1). Parallactic second may sound like a unit of time but it is not.
A parallactic second is used to measure the apparent shift of a star as seen from opposite sides of Earth‘s orbit around the sun. This movement, caused by the angle at which we view stars, can then be converted into distance. And so, it is considered as a unit of distance in astronomy. 1 parsec is equal to 3.26 light-years.