下面是一道选择题,请在第一空里填正确答案,第二空中分析句子成分。第二空答题格式如下: S: I, V: like, O: apples 间接引语用IO表示,直接引语用DO表示, 宾语补语用OC表示, 状语用A表示。 ____ is the center of out planetary system was a difficult concept to grasp in the Middle Ages. A. It is the sun and not the earth B. Being the sun and not the earth C. The sun and not the earth D. That the sun and not the earth