Question

When a star moves away from Earth, its electromagnetic spectrum stretches to make its wavelengths appear longer. Which of these methods makes use of this phenomenon to measure accurately the distance from Earth to a star?

a. Doppler Effect
b. Parallax Method
c. HR Diagram
d. Blue Shift

Answer 1

the answer is

Step-by-step explanation:

A. Doppler Effect

Answer 2

It's the Doppler effect.
But it's not used to measure the "distance from Earth".
It's used to measure how fast the star is moving away from Earth.