Answer 1

There are 3 objects here, that is why.

0) The object mybd in main.
1) The object bd of class Human.
2) The object b which is a formal parameter to Human's constructor.

First mybd is initialized, which is passed by value to Human's constructor for Daniel. Then a copy of the object is made and stored in b, which is passed to bd for data. Finally, b gets destroyed, followed by Daniel's bd and the object mybd. Thus 3 destructor calls take place.

Accepting the Birthday object by reference (normal, const or rvalue) in the constructor reduces the number of objects created.