C# increment forms: which statements correctly increase variable a by exactly 1?

Introduction / Context:
Incrementing a variable by 1 is basic, yet syntax traps are common. This question checks your understanding of valid increment expressions in C#.

Given Data / Assumptions:

• Variable a is a numeric type.
• We must add exactly 1 to the current value of a.

Concept / Approach:
Valid increment forms include the compound assignment and additive assignment. Expressions must be syntactically correct and semantically add one to the existing value of a.

Step-by-Step Solution:

Verification / Alternative check:
Compile each form. Only a += 1; and a = a + 1; compile and behave correctly.

Why Other Options Are Wrong:

• A: Invalid compound use of increment operators.
• C: Invalid grammar.
• E: Overwrites a with 1 instead of adding 1.

Common Pitfalls:
Confusing assignment with increment and misusing ++ with extra tokens.

Final Answer:
a += 1; (Note: a = a + 1; is also correct; among the given choices, both B and D increment by 1. If you must choose one, pick a += 1;.)