Prolongation is used to extend a survey line beyond existing points.

The Double-Reverse method is the most accurate as it minimizes effects of instrumental errors like non-perpendicularity of the transit axis.

Precise centering and leveling are prerequisites for all three methods.

Enables continuous surveying over long distances.

Reduces cumulative errors when using proper techniques.

Susceptible to errors in centering if not performed meticulously.

Requires professional expertise to minimize index error.

Setting out road alignments.

Railway track alignment and survey.

Large-scale infrastructure layout.

Other methods such as 'swinging the telescope' are sometimes categorized under these three main approaches based on their specific adjustments.

Option B (3) is correct because it covers the standard classification in classic surveying textbooks by authors like Punmia or Arora.