The convention is to use . . . . . . . . case for classname.

The correct answer is C. Pascal case.

Pascal case is a naming convention in which the first letter of each word in a name is capitalized. This convention is often used for variable names, function names, and class names in programming languages.

The other options are incorrect because they do not follow the Pascal case convention.

• Upper case: All letters in the name are capitalized. This convention is not commonly used in programming languages.
• Lower case: All letters in the name are lowercase. This convention is also not commonly used in programming languages.
• Mixed case: Some letters in the name are capitalized and some are lowercase. This convention is not commonly used in programming languages because it can be difficult to read and understand.