The correct answer is option 'C', which states that symmetrical wave ripples are not used for palaeocurrent analysis. Palaeocurrent analysis is the study of ancient water currents and their directions in sedimentary rocks. It is an important tool in reconstructing the depositional environments of sedimentary rocks and understanding the geological history of an area.

Here is an explanation of why symmetrical wave ripples are not used for palaeocurrent analysis:

1. Current crescents: Current crescents are crescent-shaped sand ridges formed by the flow of water in a unidirectional current. The shape of the crescent indicates the direction of the current. These structures can be used to determine the palaeocurrent direction.

2. Flute marks: Flute marks are elongated depressions or grooves formed on the surface of sedimentary rocks by the erosion of sediment by a unidirectional current. The direction of the flute marks indicates the direction of the current. These structures can be used to determine the palaeocurrent direction.

3. Imbrication of pebbles: Imbrication of pebbles refers to the arrangement of pebbles in a sedimentary rock with their long axes inclined in the same direction. This arrangement is caused by the transport of pebbles by a unidirectional current. The orientation of the pebbles can be used to determine the palaeocurrent direction.

4. Symmetrical wave ripples: Symmetrical wave ripples are small-scale, symmetrically-shaped ridges and troughs formed on the surface of sedimentary rocks by the oscillatory motion of water waves. These ripples are not formed by unidirectional currents and therefore do not provide a reliable indicator of palaeocurrent direction.

In summary, while current crescents, flute marks, and imbrication of pebbles can be used to determine palaeocurrent direction, symmetrical wave ripples are not reliable indicators and are therefore not used for palaeocurrent analysis.