标题: [求助]885-sec05-09 [打印本页] 作者: cindybig 时间: 2004-8-20 19:52 标题: [求助]885-sec05-09 9. Astronomers at the Palomar Observatory have discovered a distant supernova explosion, one (that they believe is) a type previously unknown to science. (A) that they believe is (B) that they believe it to be (C) they believe that it is of (D) they believe that is (E) they believe to be of