下列各句中“之”字意义与用法不同于其他三项的是

Nowhere in nature is aluminum found free,owing to its always with other elements,most commonly with oxygen. [ ]

I know him well_______ we have been friends since we were born.

How do you usually go to work—On foot. Walking is much than driving during the heavy traffic time.

Either you or I _____going to the teachers‘ office after class.