In Visual Basic, if you keep a variable undeclared, it is automatically taken as. . . . . . . . data type.

In Visual Basic, if you keep a variable undeclared, it is automatically taken as the Object data type. This means that the variable can hold any type of value, as Object is the base class for all data types in Visual Basic. While this can provide flexibility, it also means that the compiler won't be able to perform type checking or provide compile-time type-related optimizations for the variable. It's generally considered good practice to explicitly declare the data type of variables to ensure clarity and avoid potential issues related to type conversion.

Option A, Int, is not the default data type for undeclared variables in Visual Basic.

Option B, Char, is not the default data type for undeclared variables in Visual Basic.

Option C, String, is not the default data type for undeclared variables in Visual Basic.

Therefore, the correct option is Option D: Object.