What type of glass is typically used for cocktails that contain liquor only?

The Rocks Glass is the correct choice for cocktails that contain liquor only. This glass, often referred to as an old-fashioned glass or lowball glass, is designed for serving spirits neat or on the rocks, meaning with ice. Its short and sturdy structure allows it to hold a modest amount of alcohol, typically around 6 to 8 ounces, which is ideal for spirit-forward cocktails like whiskey or a classic Old Fashioned.

In contrast, the other options serve different purposes. The Highball Glass, for instance, is taller and used primarily for mixed drinks that involve a larger volume of mixer alongside the spirit, while the Collins Glass is also tall but specifically designed for cocktails that require more mixers, often serving drinks like Tom Collins. The Martini Glass, on the other hand, is specifically shaped for serving martinis and other cocktails that are shaken or stirred, typically without ice, using a long stem to keep the drink cool without warming it from the hand. Thus, the Rocks Glass is the most appropriate choice for liquor-only cocktails.