1 . Skin is primarily made of two layers: the uppermost layer, the epidermis, which ________ a protection against the environment; and the dermis, the layer below the epidermis.

A．is being served as

B．serves as

C．has served as

D．is served as

2 . While fossil fuels still generate roughly 85 percent of the world’s energy supply, it’s clearer than ever that the future ________ renewable sources.

A．belong to

B．is belonged to

C．has been belonged to

D．belongs to

3 . The old saying that you should live each day________ it were your last________ true.

A．even if; still proves	B．even if; is still proved
C．as if ; still proves	D．as if ; is still proved

4 . Philosophers ________back to Plato and the Ancient Greeks have given the area much thought and emphasis, and there is little doubt _________their work has helped shape the practice of education over the millennia.

A．dated, that

B．dating, whether

C．dating, that

D．dated, whether

5 . That suit ________ over 60 dollars.

A．had costed

B．costed

C．is costed

D．cost