(b) "in" cannot be a variable.
In programming, a variable is a symbolic name given to a value or an expression that can change at runtime. The value assigned to a variable can be of various data types, such as integers, floats, strings, etc.
However, "in" is a reserved keyword in many programming languages and cannot be used as a variable name because it has a specific meaning and usage in the language. For example, in Python, "in" is used as a membership operator to check if an element is present in a list or a dictionary.
Similarly, "init" is a special method in Python classes used for object initialization, and "it" and "on" are also reserved keywords or common variable names in some programming languages and may not be used as variable names.