A star is moving towards Earth. An astronomer plans to measure the distance of the star from Earth by observing the red shift in its spectrum. Which of these statements best explains why the astronomer's method of measuring the star distance is inappropriate? The spectral shift of moving stars cannot be observed. A red shift can be observed when the star moves away from Earth. Common instruments cannot measure the red shift accurately. Rate of motion of stars cannot be matched with the rate of measuring distances.