is和was都可以用。
1、Somebody was the first one to do sth.
He was the first person to set foot on the moon.
他是第一个登上月球的人。
2、sb is the first one/person to do sth
这个小男孩就是美国第一个登上月球的人-----阿姆斯特朗。
The little boy is the first American man on the moon ----- Armstrong.
is和was详细用法
is和was都是第三人称的be动词,is是现在式,was是过去式。
例如:
He is a student .(他是一个学生)。
She was a teacher .(她以前是一个老师)。
was用于I,he,she,it以及单个人作主语的句子。
例如:
I was born in 1998.
He was a doctor three years ago.