C file I/O API correctness: In the given program with three opened files, what happens when calling fclose(fp, fs, ft);?

Introduction / Context:Knowing the exact function signatures in the C standard library prevents subtle API misuse. The fclose function is designed to close a single stream at a time. Passing multiple arguments violates its prototype and leads to a compile-time error, which is important when managing several files in one function.

Given Data / Assumptions:

• Three FILE* streams are successfully opened: fp, fs, and ft.
• The code calls fclose(fp, fs, ft); with three arguments.
• Standard C header is used.

Concept / Approach:

• The prototype is int fclose(FILE stream); It accepts exactly one FILE.
• To close multiple files, invoke fclose separately for each pointer.
• Compilers type-check function calls and will reject calls with the wrong number or types of arguments.

Step-by-Step Solution:

Verification / Alternative check:

Why Other Options Are Wrong:

• Listing any subset of files as closed implies fclose can take multiple pointers, which it cannot.
• Suggesting only "A.C" closes is arbitrary and still contradicts the function prototype.

Common Pitfalls:

• Attempting to pass multiple resources to a single-argument API; instead, loop over the list and close individually.
• Ignoring fclose return values; always check for errors when closing streams.

Final Answer: