unmarked expression的用法和样例：
例句
- Reports say the hikers ignored warnings and straightly crossed the unmarked border between northern Iraq and Iran.
报告称这些旅客不顾警告直接穿越伊拉克北部和伊朗无标记的边境。 - The driver of any vehicle shall yield the right of way to a pedestrian on any portion of any unpaved road or crossing within any marked or unmarked crosswalk of a paved road.
任何交通工具的驾驶员将把右侧让给在没有铺石砖的道路任何一部分，或在铺设道路有标记的或无标记的人行横道以内的行人。
