Standard C expressions: which of the following operations is incorrect (produces a compile-time error) in ISO C?

Introduction / Context:
This question checks operator applicability across C types. The modulo operator % is defined only for integer operands. Using it with floating types is a common mistake that leads to compilation errors.

Given Data / Assumptions:

• Plain ISO C (not using fmod from math.h).
• Each statement is independent and syntactically complete.
• Implicit conversions follow the usual arithmetic conversions.

Concept / Approach:
In C, % is the remainder operator for integer types only. For floating-point remainders, you must call the library function fmod or fmodf. Assignments to self (j = j; k = k;) are valid no-ops. Integer modulo and unsigned addition are also valid.

Step-by-Step Solution:
Check each operation's operand types.(a) int % int → valid.(b) self-assignment on short → valid though pointless.(c) self-assignment on long → valid.(d) float % int → invalid; % not defined for float. Use a = fmod(a, 3.0); instead.(e) unsigned arithmetic → valid.

Verification / Alternative check:
Try compiling (d): compilers report “invalid operands to binary %”. Replacing with fmod compiles and runs correctly.

Why Other Options Are Wrong:
(a), (b), (c), (e) are legal C statements; only (d) violates operator rules.

Common Pitfalls:
Assuming % behaves like mathematical modulo for real numbers; forgetting to include math.h and link with the math library when using fmod.

Final Answer:
float a = 3.14; a = a % 3;