A.It can reduce the amount of energy needed to power appliances.
B.It can tell them how much energy each appliance is using.
C.It can allow them to turn appliances on and off when they are not at home.
D.It can reduce their electricity bills.

A.They can't be used at off-peak times.
B.They do not provide much energy.
C.They always cause system failure and blackouts.
D.They do not supply a continuous flow of energy.

A.invite
B.promise
C.divide
D.attract

A.
B.
C.
D.

A.Constructed hundreds of years ago
B.It was constructed hundreds of years ago
C.Constructing hundreds of years ago
D.To have constructed hundreds of years ago

A.piles
B.sheets
C.pieces
D.packs

A.with
B.on
C.by
D.from

A.kept pace with
B.taken into account
C.taken care of
D.made room for

A.fruit
B.seed
C.stem
D.root

A.high and low
B.thick and thin
C.collar and tie
D.null and void