Boundaries of surfaces are:
(A) surfaces
(B) curves
(C) lines
(D) points
(B) curves
Solution:
Solid is a three-dimensional object having a definite shape, size and volume is called a solid. A surface is the outermost layer of a physical object (solid). The boundaries of different surfaces are called curves. These curves are called lines when they are straight. Lines join two or more points together.
Hence, option B is correct.