Which loop snippet correctly copies n elements from src to dest?

• A. for (int i = 0; i < n; i++) dest[i] = src[i];
• B. for (int i = 0; i <= n; i++) dest[i] = src[i];
• C. dest = src;
• D. memcpy(dest, src, n);

Answer: (A)

When copying n elements, you need to touch exactly those indices from 0 up to n-1 and assign each source element to the corresponding destination element. The loop that does dest[i] = src[i] with i starting at 0 and continuing while i < n achieves this, copying every element in order without going past the end.

The other approaches break that idea in different ways. Using i <= n would try to access index n, which is outside the n-element range, leading to undefined behavior. Assigning dest = src just changes the pointers so both refer to the same memory instead of copying values. Using memcpy with a count of n copies n bytes, not n elements, so unless each element is exactly one byte, this won’t copy the intended data.