Step 1: Define a bitwise operator.
A bitwise operator performs operations on one or more binary numerals at the level of their individual bits.
Step 2: Analyze the given operators.
(A) \( \texttt{++} \): The increment operator, which increases a numeric value by one.
(B) \( \texttt{<<} \): The bitwise left shift operator. It shifts the bits of a number to the left, effectively multiplying it by a power of two. This is a bitwise operator.
(C) \( \texttt{\#\#} \): The token-pasting (concatenation) operator used by the C/C++ preprocessor.
(D) \( \texttt{\%\%} \): Not a standard operator in C/C++; the single percent, \( \texttt{\%} \), is the modulo operator.
Conclusion: The bitwise operator among the choices is \( \texttt{<<} \).