Surveying - Engineering

Q1:

The line normal to the plumb line is known as

A horizontal line

B level line

C datum line

D vertical line.

ANS:B - level line

How can you get agree with the given answer explain please?
As the level line is curved and the vertical line.
Should be perpendicular to the horizontal line only.
The correct answer should be Horizontal line only. Level line and horizontal line are same for shorter lengths only. In this case, the answer is correct. Horizontal line is the answer, if asked at all points then level line will be answer.