He was the first pianist in the 70-year history of the competition to win the prize

问题描述:

He was the first pianist in the 70-year history of the competition to win the prize

对的.
He(主) was(系动词) the first pianist (表语)in the 70-year history of the competition (表语的后置定语),to win the prize(补语).
意义:在该项比赛的70年历史上,他是第一个获得这一奖项的钢琴家.