[单项选择]Which of the following is NOT TRUE
A. None of the extra-solar planets has been seen without telescopes and they are detected directly by the effects of gravity on the motions of their mother star.
B. Calculations of the changes in motion of these stars allow astronomers to draw conclusions on the orbit of the planets, their mass and their distance from the central stars,
C. Each discovery raises new questions about the formation and behavior of planets among scientists.
D. A major problem affecting observation using current telescope technology is that light shining from the stars tends drown all weaker sources of light in the vicinity.

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