说自己是xx校友是用I am还是I was?

I was an alumnus of Sun Yan-Sen University. （不行，因为校友是个身份）

应改为：I am an alumnus of Sun Yan-Sen University.

Steve Jobs was an alumnus of Reed College. (可以，Steve Jobs已经仙游）

Bill Gates was an alumnus of Harvard University. （不可以，Bill Gates还健在）