ANS:C - to avoid long offsets from chain lines

Main line:line joining two main survey stations.
Tie line is used for surveying detail.
Check line is used for checking the work.
Base line :longest chain line. Tie line is mainly used for the joining of subsidiary lines or two offset lines. Check lines are used to check the accuracy of the work. The offset having their length more than 15m is called long offset so avoid the long offset to reduce error in chain lines. Tie or subsidiary lines: A tie line joints two fixed points on the main survey lines. It helps to checking the accuracy of surveying and to locate the interior details. Tie line is the line used to join survey line to features to avoid long offsets. It is used to check for accuracy on chain lines.