Q:

There are times so that class must "default copy c'tor" ? and what is happens while I doing "new Type[..]"?

What happens in the following line:  
Type* arr=new Type[20];  

the type Type must copy constructor or default constructor or default copy constructor?  
And again, which method is called in this line ?

A:

When you say:
 Type* arr=new Type[20];  

then enough memory to contain 20 objects of type Type. is allocated. The default constructor for Type is then called 20 times to construct each of those Type instances. If there is no default constructor for Type, (as there won't be if you defined some other constructor) then these instances cannot be constructed. 
The std::vector container doesn't have this restriction, as you can either provide parameters for its initialisation, or create objects on the fly and push them into the std::vector after the vector is created. This is one of many reasons why you should always prefer use of std::vector over allocating arrays via new.

