question: Arrange the following elastomeric impression material in decreasing order of their value of cofficient of thermal expansion:
opa: Polyether > Polysulﬁde = Addition silicone > Condensation silicone
opb: Polyether > Addition silicone = Condensation silicone > Polysulﬁde
opc: Polysulﬁde = Polysulﬁde > Addition silicone = Condensation silicone
opd: Addition silicone > Condensation silicone > Polysulﬁde > Polyether