Explanation

Creating a filter: the original sentence has an issue with the relative pronoun "which." It grammatically modifies "appliance," but that's not the intended meaning; the commands do the activating, not the appliance. Choice (A) is out. We'll look for an answer choice that corrects the error.

Applying the filter: choice (B) is defective because the phrase "in turn" indicates that the thing is shutting on and off according to some logic or sequence, whereas the intended meaning is on or off according to the each command. Choice (C) has a bad pronoun. Choice (D) uses the suspicious thereby but does so correctly. Choice (E) is defective because the verb "activates" is grammatically singular and meant to go with the grammatical subject "commands." The correct answer is (D).