托盘天平横梁上都有称量标尺和游码，向右拨动游码的作用是（） A．相当于向左调节平

a、b为正整数，且a＞b，若ab-a-b-4=0，则a=______．

She was told to give the award to whom she ever thought had contributed most to the welfare of the student body.

A．to whom she thought

B．to whoever she thought

C．to whomever

D．to him whom she thought

物体燃烧的基本要素是（）

A.火源

B.一定的空间

C.可燃烧的物体

D.充足的氧气

急性冠脉综合征

心智技能的形成要经过哪些阶段?