The first accurate measurement of the speed of light was made by Roemer in the 17th century. His measurements were based on observations of
(a) The timing of the eclipses of the binary stars Alpha and beta Centauri
(B) Refraction of light from a star when the star was eclipsed by the moon
(C) The timing of eclipses of one of Jupiter's moons
(D) The periodic eclipsing of Venus by the sun
http://en.wikipedia.org/wiki/R%C3%B8mer%27s_determination_of_the_speed_of_light
The first accurate measurement of the speed of light was actually made by Ole Rømer in the 17th century. His measurements were based on observations of the timing of eclipses of one of Jupiter's moons (Option C).
To understand how Rømer measured the speed of light, we need to delve into the details. Rømer was studying the motion of Jupiter's moon Io, which has a regular orbit around the planet. However, he noticed that the timing of Io's eclipses seemed to vary depending on the Earth's position in relation to Jupiter.
Rømer concluded that these variations were due to the finite speed of light. When the Earth was closer to Jupiter, the light from Io had less distance to travel, resulting in earlier observed eclipses. On the other hand, when the Earth moved farther away from Jupiter, the light took longer to reach us, causing a delay in the observed eclipses.
By carefully studying the observed timings of the eclipses and comparing them to the predicted timings based on the Earth's position, Rømer was able to estimate the speed of light. He found that the light took about 22 minutes to travel a distance equal to the diameter of Earth's orbit around the Sun.
Although Rømer's estimation of the speed of light was not entirely accurate by today's standards, his work laid the foundation for future measurements and the development of more precise techniques.