Python provides the built-in function `type()` to determine the data type (more precisely, the class) of an object. Because Python is dynamically typed, variable names are references to objects, and the object itself carries its type information at runtime. Calling `type(bmi)` returns a type object such as ``, ``, or `` depending on what value is currently bound to the name `bmi`. This is the standard, textbook-approved method for checking an object’s type in Python.

Option C, `typeof(bmi)`, is common in JavaScript, not Python. Options A and B are not standard Python built-ins; they might exist in user code or other languages, but not in Python’s core language. In typical coursework and professional usage, `type()` is the correct function.

Textbooks also discuss how `type()` differs from `isinstance()`. While `type()` directly reports the object’s class, `isinstance(bmi, float)` is often preferred when you want to allow subclass relationships. For example, in object-oriented programming, a subclass instance should often be treated as an instance of its parent class, which `isinstance` supports. However, when the question asks specifically for the function used to “check the data type,” the expected answer is `type()`.

# Understanding type inspection helps with debugging, writing robust functions, and reasoning about operations that are valid for different data types.