57。 Once positioned in space, the Hubble Space Telescope will capture light from sources twenty times fainter compared to those that can be detected by ground-based instruments. (A) compared to those that can b detected (B) compared to those they can detect (C) than that can be detected (D) than those that can be detected (E) than those detecting 这道题我在C与D中徘徊,还是选错了, D正确,那末those应该指代sources, 那末这里的than得比较在句子中做什莫成分呢?