What forms of control can all C programs be written using?

The correct choice identifies the fundamental control structures common to all C programs: selection, iteration, and sequence.

Selection allows the program to choose different paths of execution based on certain conditions (e.g., using if statements), thus enabling decision-making within the code. Iteration facilitates the repetition of code blocks, allowing actions to be executed multiple times (e.g., using for or while loops). Sequence refers to the linear execution of statements, where instructions are performed one after another in the order they are written.

These control mechanisms are essential to programming in C as they enable developers to structure their code logically, manage the flow of execution, and implement functionality that can adapt to varying inputs. Understanding these basic control structures forms the foundation for more complex programming concepts and practices.