String and StringBuilder in C#.NET: select the correct statements. 1) Two strings can be concatenated using s3 = s1 + s2; 2) String is a primitive in C#.NET. 3) A string built with StringBuilder is mutable. 4) A string built with String is immutable.

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Solve this multiple-choice question and choose the correct option.

Accepted Answer

Introduction / Context:This question reviews fundamental properties of string and StringBuilder and the standard concatenation syntax in C#. Given Data / Assumptions: Statements to validate include concatenation forms and mutability claims. Concept / Approach:In C#, strings are immutable, and the + operator concatenates strings. StringBuilder provides a mutable buffer for efficient concatenations or edits. The & concatenation operator is a VB feature, not C#. Step-by-Step Solution: 1) s3 = s1 + s2 → Valid in C#.2) 'String is a primitive' → False; it is a reference type with special handling.3) StringBuilder-built strings are mutable → True (the builder is mutable; resulting ToString() is immutable).4) Strings are immutable → True.5) s3 = s1 & s2 → Not C# syntax; false. Verification / Alternative check:Creating a StringBuilder and appending confirms mutability; attempting to modify an existing string shows it produces a new instance. Why Other Options Are Wrong:Options including 2 or 5 assert incorrect claims about primitives or use non-C# operators. Common Pitfalls:Assuming VB operators apply in C#; forgetting the performance implications of repeated + in loops. Final Answer:1, 3, 4

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