当我们几乎放弃希望时，解决方案突然出现了。

The solution suddenly ___materialized when we had almost given up hope.

在魔术表演中，一只鸽子突然凭空出现在舞台上。

During the magic show, a dove ___materialized out of thin air on the stage.

经过多年的研究，他的理论终于具体化为一本专著。

After years of research, his theory finally ___materialized into a monograph.