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A
Any glass of any size
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B
An amount containing roughly the same quantity of pure alcohol — e.g., about 12 oz of regular beer, 5 oz of wine, or 1.5 oz of distilled spirits
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C
Only a shot of liquor
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D
Only a pint of beer
Why this is the answer
A standard drink is defined by its alcohol content rather than its container, and different beverages reach that amount at different volumes: roughly 12 ounces of regular (about 5% ABV) beer, 5 ounces of (about 12% ABV) wine, and 1.5 ounces of (about 40% ABV) distilled spirits each contain a similar amount of pure alcohol. Servers should be aware that strong cocktails, large pours, or high-ABV craft beers can contain more than one standard drink, meaning a customer may be consuming more alcohol than the number of 'drinks' suggests.
Source: Responsible Beverage Service — Standard Drink