9. People are harmed by noise pollution but don’t even realize it. Many don’t evenknow there are two kinds of silence in us. One is internal, a feeling of respect forlife, which is at the level of the soul. The other is ________, the feeling whenhumans put themselves into a natural environment without modernity or intrusionby manmade sounds.
(A) inbound
(B) outbound
(C) extent
(D) external