Have you ever wondered why birds sing? Maybe you thought that they were just happy.  After all，you probably sing or whistle when you are happy.

Some scientists believe that birds do sing some of the time just because they are happy. However，they sing most of the time for a very different reason. Their singing is actually a warning to other birds to stay out of their territory.

Do you know what a ’territory’ is? A territory is an area that an animal，usually the male，claims(声称)as its own. Only he and his family are welcome there. No other families of the same kind are welcome. Your garden and house are your territory where only your family and friends are welcome. If a stranger should enter your territory and threaten(威胁)you，you might shout. Probably this would be enough to frighten him away.

If so，you have actually scared the stranger away without having to fight him. A bird does the same thing. But he expects an outsider almost any time，especially at nesting(筑巢)season. So he is screaming all the time，whether he can see an outsider or not. This screaming is what we call a bird’s song，and it is usually enough to keep an outsider away.

Birds sing loudest in the spring when they are trying to attract a mate and warn others not to enter the territory of theirs..

You can see that birds have a language of their own. Most of it has to do with attracting mates and setting up territories.

小题1: Some scientists believe that most of the time bird’s singing is actually _______.

A．away of warning

B．an expression of happiness

C．an expression of anger

D．away of greeting小题2:What is a bird’s "territory"?.

A．A place where families of other kinds are not accepted.

B．A place where a bird may shut at the top of its voice

C．An area for which birds fight against each other.

D．An area which a bird considers to be its own.小题3: Why do birds keep on singing at nesting season?

A．Because they want to invite more friends.

B．Because they want to find outsiders around.

C．Because their singing helps frighten outsiders away.

D．Because their singing helps remove their fears.小题4:How does the writer explain bird’s singing?

A．By comparing birds with human beings.

B．By reporting experiment results.

C．By describing birds’ daily life.

D．By telling a bird’s story.

阅读下列说明和C++代码，回答下列问题。
[说明]
某咖啡店卖咖啡时，可以根据顾客的要求在其中加入各种配料，咖啡店会根据所加入的配料来计算费用。咖啡店所供应的咖啡及配料的种类和价格如表所示。

[C++代码]
#include ＜iostream＞
#include ＜string＞
using namespace std;
consr int ESPRESSO_PRICE = 25;
const int DRAKROAST_PRICE = 20;
const int MOCHA_PRICE = 10;
const int WHIP_PRICE = 8;
class Beverage //饮料
______: string description;
public: ______() return description;
______;;
class CondimentDecorator: public Beverage //配料
protected: ______;;
class Espresso: public Beverage //蒸馏咖啡
public:
Espresso () description="Espresso";
int cost () return ESPRESSO_PRICE;
;
class DarkRoast: public Beverage//深度烘培咖啡
public: DarkRoast() description = "DardRoast";
int cost() return DRAKROAST_PRICE;
;
class Mocha: public CondimentDecorator //摩卡
public: Mocha (Beverage*beverage) this-＞beverage=beverage;
string getDescription() return beverage-＞getDescription()+",Mocha";
int cost() return MOCHA_PRICE+beverage-＞cost();
;
class Whip: public CondimentDecorator //奶泡
public: Whip (Beverage*beverage) this-＞beverage=beverage;
string getDescription() return beverage-＞getDescription()+",Whip";
int cost() return WHIP_PRICE+beverage-＞cost();
int main()
Beverage* beverage = new DarkRoast() ;
beverage=new Mocha(______) ;
beverage=new Whip (______) ;
cout＜＜beverage-＞getDescription()＜＜"￥"＜＜beverage-＞cost() end1;
return 0;

编译运行上述程序，其输出结果为：DarkRoast，Mocha，Whip ￥38。