15. Suppose p is a pointer of node points to the rear of a circular linked list. Initially, p = null.The following program codes will insert a node pointed by pointer q at the front of the circuler list. Please fill in the blanks. (A) code1: p , code2: q (B) code1: p , code2: q-＞link (C) code1: p-＞link , code2: q (D) code1: p-＞link , code2: q-＞link