Identify the correct statements about C# control statements: 1) A switch statement can act on numerical as well as Boolean types. 2) A switch statement can act on characters, strings, and enumeration types. 3) We cannot declare variables within a case unless the statements are enclosed by { }. 4) foreach should be used to change a collection to avoid unpredictable side effects. 5) All expressions of the for statement are not optional.

Introduction / Context:
This question checks nuanced C# rules for switch, foreach, and for statements.

Given Data / Assumptions:

• Five statements cover allowed switch types, scoping in case labels, foreach behavior, and for clause optionality.

Concept / Approach:
Classic C# switch does not use bool. It does support char, string, and enum. Declaring variables directly under a case usually requires braces to create scope. foreach is read-only in intent; modifying the collection during enumeration is discouraged. In C#, for(;;) is allowed, so all three expressions are optional.

Step-by-Step Solution:

Verification / Alternative check:
Language specifications and compiler behavior confirm items 2 and 3 only.

Why Other Options Are Wrong:

• 1, 2: Includes 1 (false).
• 3, 5: Includes 5 (false).
• 4, 5: Both are false.
• None of these: Incorrect because 2 and 3 are true.

Common Pitfalls:
Forgetting to use braces when declaring variables within case sections.

Final Answer:
2, 3