Sponge is to porous as rubber is to

massive
solid
elastic
inflexible

The correct answer is C. elastic.

A sponge is a porous material, meaning that it has many small holes or pores. Rubber is also a porous material, but it is also elastic, meaning that it can be stretched and then return to its original shape.

The other options are not correct because they do not describe both sponges and rubber.

  • Massive: A sponge is not massive, it is lightweight.
  • Solid: A sponge is not solid, it is a porous material.
  • Inflexible: A sponge is not inflexible, it is a flexible material.