Complete the following passage by filling one word for each blank.

If there is just one single thing more astonishing than the ability of the adult human being to talk, it is the process by which someone learns to do this. Some parts of the process are still (1)________ much a closed book, but it is for the (2)_________ part possible to describe what the child is doing at various stages in its development, even if we cannot account (3)________ how exactly it learns to do these things. In fact, research carried out by various linguists has (4)_________ rise to as many theories as there are differences in the rate of development. A baby actually makes sounds from the moment it is born, but for some time these are rather far removed (5)_________ articulate speech. In something like a year, a baby will probably be at a stage where one or two syllables represent the peak of its achievement as a speaker; one more year and it will be (6)_______ out with short phrases, and after this it seems (7)________ time at all before the child is capable of uttering complete sentences.           Despite being a truly remarkable feat of learning, this is one that is performed by the vast (8)_________ of human beings. Complex operations are brought (9)________ play in these dealing with speech and language; the key (10)_______ in brain work, though tongue – work and ear – work play a part in the whole process.

Some parts of the process are still (1)________ much a closed book, but it is for the (2)_________ part possible to describe what the child is doing at various stages in its