他计划明年申请洪堡大学的研究生项目。

He plans to apply for a graduate program at ___Humboldt next year.

洪堡是19世纪最重要的自然科学家之一。

___Humboldt was one of the most important natural scientists of the 19th century.

我们计划下个月去洪堡县看红木森林。

We're planning to visit the redwood forests in ___Humboldt County next month.