Which of the following variables and functions can be used together to create a useful object type?

The correct choice emphasizes the significance of related variables and functions to form a cohesive object type, which enhances data organization and functionality.

In the selection that features "student_marks," "student_name," and "calculate_average()," all elements are inherently linked to the concept of a student. The variables represent attributes of a student, specifically their name and marks. The function "calculate_average()" is crucial as it operates on the student_marks to determine a meaningful statistic, further integrating these components to create a dynamic and useful object type that could represent a student entity thoroughly.

Such an object type would be able to encapsulate both data (the student's name and their marks) and behavior (the ability to calculate average marks), which is a core feature of object-oriented programming. This encapsulation allows for easier management and manipulation of related data, making it more intuitive to work with.

The other options, while they contain variables and functions, either do not share a meaningful connection that would allow for a coherent object type or consist of variables that relate to entirely different contexts, which diminishes their utility as a combined object type. For example, combining variables related to cooking ingredients with unrelated concepts like weather fails to form a cohesive structure that benefits from an object-oriented approach.