A default constructor

takes no arguments
has default values for all its arguments
either (a) or (b)
neither (a) nor (b)

The correct answer is: A. takes no arguments.

A default constructor is a special constructor that is called when an object is created without any explicit constructor being called. It has no parameters and is always available, even if you do not define one yourself.

The other options are incorrect because:

  • B. has default values for all its arguments is incorrect because a default constructor does not have any arguments.
  • C. either (a) or (b) is incorrect because only A is correct.
  • D. neither (a) nor (b) is incorrect because A is correct.