选择题：A new kind of machine (21) to take the place of hu

A new kind of machine (21) to take the place of humans.These machines can do jobs that are too
dangerous for humans.
(22),they are being developed to work in nuclear power centers,deep waters and outer space.
This is how the new machines work.A machine is placed in an area far away from the person who
controls it.The person wears a special hard hat with tiny television screens.The screens
(23) the person see and hear exactly what the machine is seeing and hearing.This gives the person the feeling of being in the same place_
(24) the machine.The person controls the machine.The machine follows thepesor.s nouenenls cuctly,If the reron raises his ritht am, the modhine aine the ragle arn twoker can do a daungerous job while_(26) in a sate place.Forexample,a pThis means an
(25)can direct the machine (27) a bomb (28) going near the bomb himself. The ney machines are not exactly (29) robots.Robots are controled by a computer.The row
machines are controlled by a person.The new mechines are called teleoperators.The nuedlear pone industry is especially interested in teleoperators.The machines could solve the problem of (30) radioactive materials.
21.A.is developing
B.has developed
C.develops
D.is being developed
22.
A.For example
B.Such as
C.If
D.And so on
23.
A.let
B.enable
C.cause
D.allow
24.
A.of
B.like
C.as
D.for
25.
A.experiencing
B.experienced
C.experi