If a bimetallic strip is heated then when the strip is vertical 

• A

  higher $\text{'}\alpha \text{'}$  material gains concave shape

• B

  higher  $\text{'}\alpha \text{'}$ material loss concave shape

• C

  higher $\text{'}\alpha \text{'}$  material gains convex shape

• D

  higher $\text{'}\alpha \text{'}$  material loss convex shape