题目

Word came ________ Chang'e­Ⅱ was Launched successfully and carried out the task as expected. A．which     B．what C．when      D．that 答案：解析;that引出同位语从句，无意义，也不充当句子成分。 答案;D9．如图，已知AB为圆O的直径，C，D是圆O上的两个点，C是劣弧$\widehat{BD}$的中点，CE⊥AB于E，BD交AC于G，交CE于F．（1）求证：CF=FG（2）求证：DG•AC=AG•CE．