twois one plus one 1Because 2 = + 1
Some examples are
biker
laker
dancer
A. the girl in blue looked pretty. it’s the only one that makes since
In the sentence "Radio, the earlier invention, gave listeners only sound" there are four nouns, thus four possible objects: Radio, invention, listeners, and sound.
Radio is the subject which "gave" the indirect object "sound" to the direct object "listeners."