빈칸 (A)와 (B)에 들어갈 말로 가장 적절한 것은?


During the 1950s, the large and heavy valves in the
radio began to be replaced by small transistorized
electronic components that required less electrical power.
On account of this, receivers could operate from
batteries and as a result radio sets became smaller and
lighter. Individuals could take their transistor radios with
them, whether into the privacy of the teenage bedroom
or down to the beach. At the same time, radios also
became an integral feature of the car. The listeners were
no longer thought of as a stationary group listening in
the home or crowded public place. Further improvements
in transmission techniques and modifications to the
quality of microphone technology enabled broadcasters
to introduce a style of address that was more intimate
and which spoke to the individual as the sole listener.

The development in radio-related technology helped
increase the ____(A)____ of the radio and led
broadcasters to talk to listeners in a more ____(B)____
way.


(A)            (B)
① mobility personal
② ownership respectful
③ contribution personal
④ mobility systematic
⑤ ownership systematic