An amateur astronomer thinks he may have seen unusual event in the sky he needs to describe the location to a nearby servatory which of the following should he use

One astronomical unit is equal to the distance from Earth to the Sun. The second option among all the options given in the question is the correct option. The distance as calculated in the year 2012 by the International Astronomical Union was equal to 149597870700 meters. Astronomers like to use this unit for measuring the distances between planets and other solar bodies.