The answer is "measure the parallax and use it in calculations".
Explanation:
In this question, the above choice is correct because, in the summer and winter, light is observed from both parts of a planet. An astronomer can once, again and 6 weeks later calculate the position of a star and then compute the perceived shift of location. It measures which utilizes parallax and its best method for calculating the approximate distance between the star, as well as the planet.
