Which of the following material is highly resistant to flexure and fractures suddenly when stressed?

The set impression materials can be rigid (inelastic) or elastic. A set rigid material is highly resistant to flexure, and it fractures suddenly when stressed, in a manner similar to that of chalk. Material is not flexible and will fracture when deformed, like chalk. ZOE impression paste, impression plaster, and impression compound are inelastic impression materials. The term elastic means that the material is flexible and can be deformed and still return to its original form when unstressed. Examples include agar, alginate, and elastomers.