Today, astronomers can detect and measure stellar parallax for thousands of the nearest stars, providing us with direct evidence that Earth really does orbit the Sun. Moreover, as the Parallax Angle animation shows (return to the main "Parallax" screen, and select the "Parallax and Distance" button), these measurements allow us to calculate distances to these relatively nearby stars. If we hope to use parallax to measure distances to even more-distant stars, which of the following telescopes would be most useful?
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a. An extremely large telescope built at the best observing site on Earth
b. A larger version of the Hubble Space Telescope, placed in Earth orbit
c. A telescope placed on the same orbit of the Sun as Earth, but on the opposite side of the Sun
d. A telescope that orbits the Sun in the outer solar system