如图所示的杠杆(自重和摩擦不计),O为支点,A处挂一重为100N的物体,为保证杠杆在水平方向平衡,在中点B处沿____ (F或F1或F2)方向施加一个最小的力为____ N.
Can you tell _______ the way to the ocean? ( )
He felt very happy, because he ______ the exam.
从文中看出,什么是真正的格物致知精神?