C#.NET data types — which statements are correct? 1) Each value type has an implicit default constructor that initializes the type's default value. 2) A value type can contain the null value. 3) All value types implicitly derive from System.ValueType. 4) It is not essential that local variables be definitely assigned before use. 5) Variables of reference types store references (not the actual object data).

Introduction / Context:
Correctly distinguishing value types and reference types in C#.NET is foundational for understanding memory behavior, default values, and assignment semantics.

Given Data / Assumptions:

• We consider standard C# rules (definite assignment, default values).
• Nullable value types (T?) are not implied unless explicitly stated.

Concept / Approach:
Value types (structs, built-in numerics, bool, etc.) have an implicit parameterless constructor provided by the runtime that produces the type's default value (e.g., 0 for numerics, false for bool). All value types derive from System.ValueType. Reference-type variables store references to objects. Non-nullable value types cannot hold null; definite assignment requires locals be assigned before use.

Step-by-Step Solution:

Verification / Alternative check:
Inspect IL or use default keyword: int x = default; compiles and initializes x to 0.

Why Other Options Are Wrong:
They contradict definite assignment or nullability rules.

Common Pitfalls:
Assuming one may define custom parameterless constructors for structs (historically disallowed) or that locals auto-initialize like fields (they do not).

Final Answer:
1, 3, 5