There is___“r”and    “u” in “run”.[ ]

A.an ; a

B.a ; an

C.an ; an

D.a ; a

双链表的每个结点包括两个指针域。其中rlink指向结点的后继，llink指向结点的前驱。 如果要在p所指结点前面插入q所指的新结点，下面操作序列正确的是______。

A．p↑.rlink↑.llink:=q; p↑.rlink:=q; q↑.llink:=p; q↑.rlink:= p↑.rlink;

B．p↑.llink↑.rlink:=q; p↑.llink:=q; q↑.rlink:=p; q↑.llink:= p↑.llink;

C．q↑.llink:= p; q↑.rlink:= p↑.rlink; p↑.rlink↑.llink:=q; p↑.rlink:=q;

D．q↑.rlink:=p; q↑.llink:= p↑.llink; p↑.llink↑.rlink:=q; p↑.llink:=q;