A．Surprised.
B．Skeptical.
C．Disgusted.
D．Alarmed.

A．They can use the light more effectively.
B．They are stronger than the common materials.
C．They can store and release heat.
D．They can absorb water if necessary.

A．They become lighter when the temperature is low.
B．Their chemical composition changes with the temperature.
C．Their color darkens when the temperature is high.
D．Their structures are rearranged as the temperature fluctuates.