Answer: Transparent
Objects are classified into three types, based on the ability of light to pass through them. They are Transparent,translucent and opaque.
1. Transparent -The objects which allow all the light to pass through them are called transparent objects. Examples: Water, air, glass etc.
2. Translucent - The objects which partially allow the light to pass through them are called translucent objects. Examples: Butter paper, vegetable oil etc.
3. Opaque - The objects do not allow any light to pass through them. They make a dark shadow when light falls on them and are called opaque objects.
Examples: Wood, table, wall, pen etc
Hence, Objects that completely allow light to pass through them are called transparent.