What became of the classmates from our graduation year?

what 是疑问代词，在这里用于询问情况或结果。 became 是动词 become 的过去式，意思是"变成、成为"。 of 是介词，在这里表示"关于"或"属于"的关系。 what became of 是一个固定短语，意思是"...怎么样了？"或"...发生了什么？"，用于询问某人或某物的现状或命运。