```PASSAGE II
Where is the musical performance of songbirds held? It is not in any concert hall but rather on trees, fences and telephone wires.
It is from these places that the little feathered creatures blend their voices in some of the most melodious songs sung in the world.
Songbirds do not just make noise. The male voices in the choir, for instance, have two different messages.
Firstly, it is a warning to other males not to come near their partners. Secondly, it is an invitation from the bachelors
to the female birds. The most interesting songs which are sung with a lot of vigour are produced during the breeding
season by the males to impress the lady birds.
Songbirds are very remarkable. They sing three or four notes at a time. To the human ear it sounds like one beat but the birds can identify the different notes because of their keen sense of hearing.
At times, what is heard may not be a song of our winged friends but simply an instruction to keep the flock together.
It may also be a warning of an approaching danger.
Just how birds compose their songs is an interesting subject. Some birds have their songs fixed in their brains at birth.
Whilst some imitate others, other birds try to compose songs which are unique. They will never copy what they hear others sing.```
Unique in the passage means

• A.suitable
• B.similar
• C.exciting
• D.special