C++ constructors: which of the following is NOT a constructor type?

Introduction / Context:
Constructors initialize objects and establish class invariants. C++ recognizes several common constructor categories by usage rather than special keywords. This question checks whether you can distinguish real constructor types from invalid notions in standard C++ terminology.

Given Data / Assumptions:

• We consider standard C++ (not vendor extensions).
• Constructor names match the class name and have no return type.
• Friendship grants access; it is not a kind of constructor.

Concept / Approach:

Recognized categories include: default constructor (no parameters), parameterized constructor (with parameters), and copy constructor (takes const Class& under typical form). There is no such thing as a “friend constructor.” The friend keyword grants another function or class access to private/protected members; it does not turn a constructor into a different “type.” Constructors themselves can be friends of another class, but that does not create a new constructor category.

Step-by-Step Solution:

Verification / Alternative check:

Reviewing language references shows friend applies to functions/classes for access control. A constructor may be declared friend of another class, but its own classification remains default/parameterized/copy/move.

Why Other Options Are Wrong:

Copy constructor: initializes from another object of the same type.

Default constructor: callable with no arguments.

Parameterized constructor: accepts arguments to customize initialization.

Common Pitfalls:

• Confusing friend with constructor categories.
• Forgetting move constructors (C++11+)—not listed here but standard.

Final Answer:

Friend constructor