He devoted himself _______ to his research and got many achievements.

A．certainly

B．extremely

C．carefully

D．entirely

将含有100个结点的完全二叉树从根这一层开始，每层从左到右依次对结点编号，根结点的编号为 1，编号为71的结点的双亲的编号为______。

A．34

B．35

C．36

D．不确定