Final answer:
The question is regarding the behavior of a Turing machine that halts when started on an empty tape; the provided options do not include a direct action that results in halting, and seem to be flawed as they describe actions taken during computation, not the halting state itself.
Step-by-step explanation:
The question asks about the behavior of a Turing machine that halts when started on an empty tape. The correct behavior for a Turing machine to halt on an empty tape would be to enter a halting state immediately after the computation starts, without the need to perform any movements (such as moving left or right) or writes (such as writing a symbol on a blank square). Therefore, the options involving moving left on a blank symbol or writing a symbol on a blank square would not directly cause the machine to halt. Instead, they are actions that the Turing machine might take during its computation based on its transition functions, but not necessarily actions that would lead to a halting state from the start on an empty tape. Option (c) 'Enters a non-halting loop' is incorrect as it specifies a non-halting behavior, which contradicts the requirement for the machine to halt. A machine that halts should enter a halting state without entering any loop, thus stopping its operation. Since none of the provided actions describe a machine directly entering a halting state, the question seems to contain a flaw as it does not provide an action that would directly result in the halting of the Turing machine on an empty tape.