C++ Constructor - Quiz Explanation

The correct answers are indicated below, along with text that explains the correct answers.
 
1. A constructor's chief purpose is to:
Please select the best answer.
  A. allocate any array whose size is given as a constant
  B. initialize class variables
  C. construct a line of output from multiple parameters
  D. all of these
  The correct answer is B.
A constructor is an initializer for its class. A destructor is a finalizer for its class.

2. If the class does not provide an explicit constructor:
Please select the best answer.
  A. The compiler generates an error
  B. the compiler generates a default constructor
  C. the compiler initializes all class variables to 0
  D. none of these
  The correct answer is B.
In analog to native types, the compiler will create a default constructor.

3. A default constructor:
Please select the best answer.
  A. takes no arguments
  B. returns no value
  C. is created for you if you do not specify any constructors
  D. all of these
  The correct answer is D.

4. A constructor initializer:
Please select the best answer.
  A. initializes each data member to 0
  B. initializes data members with the value in parentheses
  C. calls default constructor to initialize each data member
  D. may only be used in a copy constructor
  The correct answer is B.
A constructor initializes data members with a value in parentheses, as in 
foo(int i) : a(i) { ..... }
.
The member a is initialized with i.