A penetration tester has been hired to perform a penetration test for an organization. Which of the following is indicative of an error-based SQL injection attack?

The fragment 'a=1' compares a string literal against a numeric column value, forcing the database engine to raise a type mismatch or conversion error. This error-based technique causes the database to surface diagnostic output that can reveal schema details or version information. The trailing '--' comments out the remainder of the original query to prevent syntax errors.

The '1=1' prefix is a numeric tautology that always evaluates to true without triggering an error, classifying this as a boolean-based blind injection pattern rather than an error-based one.

'1=1 or 2--' uses only valid numeric comparisons that evaluate silently without type mismatches, making it a boolean-based injection that returns a true condition rather than an error state.

Despite ending with the string 'a', the leading '1=1' tautology classifies this as a boolean-based injection; the 'a' reference is ambiguous and does not reliably produce a typed database error the way a string-to-integer comparison does.