As time goes on, the mountainous topography is worn down, the stream valley becomes wider, and the stream begins develops bends. These characteristics are typical of what are called stage streams.

The old age stage streams.

Explanation:

The streams can be defined as a flow of water downhill when excess of water is shed from rainfall or snowmelt. The development of streams is divided into three stages the young stage, the mature stage, and the old age stage.

The stage in which the stream valley becomes wider is the old age stage.

The old age stage is the last stage of the three stages. In this stage, the streams slows down and begin cuttting down wider valley. The stream in this stage begiins to cut down the valley in wider range and equally. The stream begins to develop bends in this stage.

So, the correct answer is the old age stage stream.