The correct answer is option 4: Hanging valleys are not formed by the depositional activity of glaciers.

Let`s dissect each option to understand why option 4 is the correct answer:

Option 1 states that cirques result from glacial erosion. A cirque is a steep-walled, amphitheater-shaped hollow that is usually found at the head of a glacial valley. Glacial erosion occurs as glaciers move and scrape the land, resulting in the formation of cirques, so this statement is correct.

Option 2 states that glacial erosion gives rise to glacial troughs or U-shaped valleys. Glacial erosion refers to the process where glaciers modify the landscape by scraping and plucking rocks. As glaciers move down valleys, they erode the sides and bottoms, forming U-shaped valleys or glacial troughs. Therefore, this statement is correct.

Option 3 states that glacial topography is parasitic in nature. Parasitic refers to something that feeds off a host and harms it. In the context of glacial topography, the term "parasitic" is incorrect. Glacial topography refers to the landforms created by glaciers, such as moraines, drumlins, and eskers, which are not harmful or detrimental to the landscape