Correct option is A
A
Bench Mark is a relatively permanent point of reference with a known elevation concerning an assumed datum, such as Mean Sea Level. It is used as a starting or reference point for leveling operations in surveying.
·
Mean Sea Level: This is a general datum used to measure elevations, not a specific reference point.
·
Ground Level: Refers to the natural surface of the earth, not a fixed reference point.
·
Level Line: Refers to a line in which all points have the same elevation, not a permanent reference point.
·
