In C++ source code, which characters begin a single-line comment so that the remainder of the line is ignored by the compiler?

Introduction / Context:
Comments are essential for documentation and maintainability. C++ supports two primary comment styles: single-line comments and block comments. Knowing the correct introductory tokens prevents syntax errors and ensures that annotations do not accidentally become part of the program logic.

Given Data / Assumptions:

• The code is compiled as C++ (not strictly C89).
• We focus on the most common, single-line comment style used in modern C++.
• No preprocessor tricks or unusual compiler extensions are considered.

Concept / Approach:
In C++, the token // begins a single-line comment. Everything from // to the end of that physical line is ignored by the compiler. C++ also supports block comments beginning with /* and ending with / for multi-line remarks. Symbols such as , &&, backslash, or at-sign have other syntactic meanings and do not introduce comments.

Step-by-Step Solution:
Identify the desired behavior: comment out the remainder of a single line.Recall that the correct token in C++ for single-line comments is //.Place // before the text to be ignored.Confirm that the compiler discards the trailing text and proceeds with parsing the next line.

Verification / Alternative check:
Create a minimal program that contains code, a // comment, and a statement on the next line. Observe that only the code outside comments is compiled. Replacing // with other tokens will either cause compilation errors or change program meaning (for example, && is a logical operator).

Why Other Options Are Wrong:

• and && are operators or text without comment semantics.
• \\ is an escape for a single backslash in string literals; it does not start comments.
• @ has no standard meaning for comments in C++.

Common Pitfalls:
Accidentally nesting block comments with / and */ can cause unexpected uncommenting. Using // avoids nesting issues for single lines.

Final Answer:
//.