Which of these cocktails is stirred gently, but not shaken?

The Negroni cocktail is made of one part gin, one part vermouth rosso (red, semi-sweet), and one part Campari, garnished with orange peel. It is considered an apéritif.

While the drink's origins are unknown, the most widely reported account is that it was first mixed in Florence, Italy, in 1919, at Caffè Casoni (formerly Caffè Giacosa), located on Via de' Tornabuoni and now called Caffè Roberto Cavalli. Count Camillo Negroni concocted it by asking the bartender, Fosco Scarselli, to strengthen his favorite cocktail, the Americano, by adding gin rather than the normal soda water. The bartender also added an orange garnish rather than the typical lemon garnish of the Americano to signify that it was a different drink. Since the drink was conceived before the invention of dry gin, the kind of gin used would have likely been barrel aged or Old Tom style.

The preparation is to stir into a glass over ice, garnish and serve.

The other three cocktails preparation is to pour all ingredients into cocktail shaker filled with ice and shake.