The correct answer is option 4: mountain system. Cordillera in North America refers to a major mountain system that stretches along the western coast of the continent. This mountain system consists of a series of ranges, including the Rocky Mountains, Sierra Nevada, and Coast Mountains, among others.

Option 1 is incorrect because Cordillera is not a river basin. A river basin refers to the area of land where all the water drains into a specific river and its tributaries.

Option 2 is also incorrect because Cordillera is not a high plateau. A plateau is a flat, elevated landform with steep sides, while Cordillera is composed of mountain ranges with varying elevations.

Option 3 is incorrect as well because Cordillera is not an inland lake. An inland lake is a body of water that is completely surrounded by land, whereas Cordillera is a landform consisting of mountains.

Therefore, the correct answer is option 4: mountain system. Cordillera in North America refers to a vast network of mountain ranges that span across a significant portion of the western coast of the continent.