Which unit represents a pound as an abbreviation?

The abbreviation for a pound is represented as "lb." This abbreviation comes from the Latin word "libra," which means scales or balance and refers to the unit of measurement for weight. Traditionally, the term has been used in various contexts in the English-speaking world and remains a standard representation of weight measurement in both the imperial and customary units.

The other options represent different units of measurement: "kg" stands for kilograms, a metric unit of weight; "g" stands for grams, which is also a metric unit of weight; and "qt" stands for quarts, which is a unit of volume. Each of these options pertains to weight or volume, but "lb" is specifically the recognized abbreviation for pounds.