Answer: Never was she so enchanting as at this time, when she recalled the sunshine of her smiles and spent them upon us.—Shelley, Frankenstein
Explanation: The last option is the one that uses syntax for emphasis. In fact, the strategy used by the writer to give more emphasis is called "Inversion". Inversion means that the writer puts the verb before the subject. Even though inversion is mainly used to ask questions, it is sometimes used as a way of emphasizing a structure. In the example given the writer uses syntax to emphasis the following phase: "Never was she so enchanting as at this time" (the verb WAS is before the subject SHE)