题目内容：

    HOW BIG should a business team be?It is an enormously important issue for companies, Teams that are too small may lack the skills required to get the job done:teams that are too big may be impossible to co-ordinate.

Robin Dunbar.an anthropologist at Oxford University,has done a lot of work on primate(灵长目）groups.His argument is that the size of the group is linked to the size of the brain.With their large brains,humans can cope with larger bands,A larger social group has many advantages,allowing for greater protection and specialization.

Whereas 150 is sometimes referred to as the"Dunbar number",the academic himself in fact refers to a range of figures.He observes that humans tend to have five intimate friends,15 or so good friends,around 50 social friends and 150-odd acquaintances.

Running a larger network can be difficult.The armed forces have spent more than 1,000 years experimenting with unit size.A Roman centurion(百天长）oversaw 100.The modern American army company has 180 members.Britain's equivalent numbers 120.These are rough estimates,rather than fixed figures.But it is striking that many group activities seem to be close to a Dunbar number. The Special Air Service of Britain has four-man patrols;when your life depends on it,you need to have absolute trust in your colleagues.As a result,such groups are limited in size.

For much of economic history,work was conducted in small units by peasants,tenant farmers and craftsmen.The coming of powered machinery enabled production at a much larger scale,with workers crowded into factories.These days the rise of the service economy means that workers are no longer concentrated in such large groups.

This may not be a bad thing.It was easy for employees in large factories to regard remote company owners as "them"rather than"us".The modern company may settle on a model with a small group of"core"workers and a larger group of contract workers.The result may be more united within the core staff but the non-core staff may be less well treated.The small core teams may work effectively.The big question will be the effect on morale of those outside those teams.

1.What does the first paragraph serve as in the whole article?

A.An example of the topic,

B.An introduction to the topic,

C.A guide to the whole article,

D.No relation to the passage at all.

2.What does the underlined"This"in the last paragraph refer to?

A.Workers crowded into factories

B.'These days the service economy has risen.

C.Workers are no longer concentrated in such large groups.

D.Employees regard company owners as"them"rather than"us".

3.What is probably the best model for a company according to the author?

A.A large group of exact 150 workers.

B.A small group of less than 15 core workers.

C.A small group of peasants and a large group of factory workers.

D.A small group of efficient workers and more contract workers.

4.What is the main purpose of writing the text?

A.To offer companies some useful advice.

B.To introduce us the most suitable size of teams.

C.To arouse the readers' interest in Robin Dunbar.

D.To persuade companies to adopt the"Dunbar number".