Two rods of different materials having coefficients of thermal expansion ${\alpha }_1$and ${\mathrm{\alpha }}_2$ and Young's moduli Y₁ and Y₂ respectively are fixed between two rigid massive walls. The rods are heated such that they undergo the same increase in temperature .There is no bending of the rods. If a1 and a2 are in the ratio 2 : 3, the thermal stresses developed in the two rods are equal provided Y₁ : Y₂ is equal to:

• A

  2 : 3

• B

  1 : 1

• C

  3 : 2

• D

  4 : 9