Answer True of False to the following statements.

a. Above its glass transition temperature, a polymer is glassy and brittle.
b. Below the glass transition temperature, polymer chains lose their mobility (they are less capable of bending, flexing, raveling, and rotating about covalent bonds along the backbone.
c. The glass transition temperature of a material is normally above its melting temperature.
d. The elastic modulus of a polymer decreases when it is heated above its glass transition temperature