Solar energy is not only plentiful and infinite but also clean and safe.
A.uncountable
B.boundless
C.inflexible
D.unlimited

Oil, coal and natural gas are ______ fuels made from decayed material from animal or plants.
A.solid
B.smokeless
C.unleaded
D.fossil

Hydroelectric power is produced by the fall of water trapped in a _____.
A.dam
B.factory
C.river
D.city

The natural environment consists _____ all natural resources.
A.in
B.on
C.at
D.of

Dry cleaning is the _______ by which clothes are cleaned in liquids other than water.
A.conduction
B.progress
C.procedure
D.process

Choose the correct answer to complete each sentence.Can you answer the phone? ________ is calling.
A.Someone
B.No one
C.Noone
D.Everyone

There was _________ inside. The building was empty.
A.no one
B.everyone
C.someone
D.one

All the guests were dancing. _______ having a good time.
A.All was
B.Every was
C.Someone were
D.Everyone was

There is an exam tomorrow. Needless to say, _______ has to study for it.
A.everything
B.someone
C.everyone
D.anyone

I certainly hope that David is aware ______ all the problems imvolved.
A.in
B.of
C.at
D.on