Concept:
Fluvial landforms are those created by the action of running water, that is by rivers and streams. The way a river erodes its channel produces characteristic shapes.
Step 1:
Recall how each landform is made. U-shaped valleys are carved by glaciers (glacial), pediments are gently sloping bedrock surfaces formed in arid regions, and sand dunes are built by wind (aeolian). None of these are river features.
Step 2:
A river in its youthful stage cuts downward (vertical erosion) faster than it widens its banks, which produces a steep, narrow V-shaped valley. This is a classic fluvial (river-made) landform.
Answer: Option (2) — V-shaped valleys.