16. Suppose p is a pointer of node points to the rear of a circular linked list. Initially, p = null. Suppose we have another linked list pointed by avail which links the unused space together. The following program will erase the circular list into the single linked list pointed by avail. Please fill the blanks.(A) code1: p-＞link-＞link, code2: p (B) code1: p , code2: p-＞link-＞link (C) code1: temp , code2: avail (D) code1: avail , code2: temp