Antonyms — Choose the option that gives the opposite of ‘‘HOLLOW’’ (structure/material sense: empty cavity vs. solid mass).

Given data

• Term: HOLLOW
• Options: Filled; Solid; Strong; Substantial

Concept/Approach
As an adjective for objects, ‘‘hollow’’ means having an empty space inside.The standard antonym is ‘‘solid’’—without internal cavities.

Step-by-step reasoning
Hollow (cavity inside) ↔ Solid (no cavity).‘‘Filled’’ is the opposite of ‘‘empty’’ rather than the structural adjective ‘‘hollow’’; an object can be hollow yet filled with something.‘‘Strong’’/‘‘Substantial’’ concern strength/amount, not internal voids.

Verification/Alternative
Dictionary pairing often gives hollow–solid as canonical antonyms.

Common pitfalls
Choosing ‘‘Filled’’ due to confusion with ‘‘empty’’; here the key is structural property.

Final Answer
Solid