Option 3 is the odd one out — and its body does not execute even once.

Take each in turn.

Option 1. while (1) tests the constant 1, which in C is always true, and nothing inside the body ever changes that. i increments for ever (overflowing along the way, which is undefined behaviour but does not end the loop). Infinite.

Option 2. for ( ; ; ) omits all three expressions. An omitted condition in a for header is defined by the language to be true, so this is the idiomatic C infinite loop, more compact than while (1). Infinite.

Option 3. t is initialised to 0. A while loop tests before it enters, and 0 is false in C, so control passes straight over the body — f = 1; never runs. The loop terminates immediately. Not infinite — the answer.

Option 4. A do-while runs its body first and tests afterwards. x is 0 and only y is assigned inside, so x == 0 is true on every test and the loop never ends. Infinite.

The two ideas being tested are worth separating. First, C has no boolean type in the classical sense: any non-zero value is true and only zero is false, so while (t) with t zero is simply while (false). Second, while is a pre-test loop and do-while a post-test loop — which is exactly why options 3 and 4, superficially similar, behave oppositely: swap their loop forms and the answers swap too.

A classic trap the question avoids but is worth noting : writing while (x = 0) with a single equals sign assigns rather than compares, yielding 0 and so terminating — a bug that compiles cleanly. Option 4 correctly uses ==.

Hence, the loop that is not infinite is option 3.