An international team of astronomers has discovered 11 new planets outside the solar system, raising fresh ______ about the possibility of life in outer space.

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.

A．discoveries of new planets set scientists thinking
B．extrasolar planets exist in the universe
C．solar system should be re-examined by mankind
D．new discovery depends on new theory