Which of the following is used as a mixer in the Lemon Drop Martini?

The Lemon Drop Martini typically features a bright, tart flavor profile that is enhanced through the use of a mixer. The correct choice, which includes a splash of Sprite and sour mix, captures this essence well. Sprite adds sweetness and a light carbonation, which balances the tartness of the lemon juice, creating a harmonious blend. The sour mix contributes additional acidity and sweetness, further complementing the lemon flavors present in the martini.

In this context, it's important to note that the other options would not deliver the same balance or flavor profile that is traditionally sought after in a Lemon Drop Martini. A splash of lime juice, while it could provide acidity, doesn't contribute the same degree of sweetness that enhances the drink. Orange juice would introduce a different fruit flavor that deviates from the lemon-centric character of the cocktail. Tonic water, with its distinct bitterness, would overwhelm the intended flavor profile rather than complement it. Therefore, the splash of Sprite and sour mix is the best choice for achieving the desired taste in a Lemon Drop Martini.