这片土地几十年来一直未被开发，保持着原始的自然状态。

The land has remained ___unimproved for decades, preserving its natural state.

这块未开发的土地非常适合野生动物栖息。

This ___unimproved land is perfect for wildlife habitat.

他的钢琴技巧多年未经练习，依然生疏。

His piano skills remained ___unimproved after years without practice.