A treadle bar is used for A. interlocking points and signal B. setting points and crossings C. setting marshalling yard signals D. track maintenance

The correct answer is: A. interlocking points and signal.

A treadle bar is a type of lever that is used to control the movement of railway points and signals. It is typically made of steel and has a footplate that is used to activate it. When the treadle bar is pressed down, it causes a lever to move, which in turn controls the movement of the points or signals.

Treadle bars are used in a variety of railway applications, including interlocking systems, point machines, and signal boxes. They are also used in some types of track maintenance equipment.

Here is a brief explanation of each option:

• Option B: setting points and crossings. Points are the parts of a railway track that allow trains to change direction. Crossings are the parts of a railway track where two tracks cross each other. Treadle bars are not typically used to control the movement of points and crossings.
• Option C: setting marshalling yard signals. A marshalling yard is a railway yard where trains are sorted and assembled. Signals are used to control the movement of trains in a marshalling yard. Treadle bars are not typically used to control the movement of signals in a marshalling yard.
• Option D: track maintenance. Track maintenance is the process of keeping railway tracks in good condition. Treadle bars are not typically used in track maintenance.