Read the passage carefully and answer the question that follows.

Birds are found almost everywhere, even in the hearts of the cities and because they are active creatures, they easily lend themselves to study. One of the first things that a child notices is how noisy many kinds of birds are. The guinea fowls are renowned for this. Even while they are feeding, many birds make characteristic calls, and with practice you can tell which species are in a wood just from these calls without seeing the birds at all. Clearly this continuous chatting is important to birds. When flocks of finches are looking for insects or seeds on the branches of trees, they could easily become separated and these calls must help keep the birds together.

There are many other occasions when birds utter calls. For example, at the sight of a bird of prey, a small bird will give its flying predator call as an alarm to other birds in the neighbourhood.

[Adapted from (1985) Objectives Test in English Comprehension, Lexis and Structure. Great Britain: William Collins Sons and co Ltd.]