Which unit is represented by the abbreviation 'ft'?

The abbreviation 'ft' stands for foot or feet, which is a unit of length in the imperial system of measurement. This measurement is commonly used in everyday applications, such as in architecture, construction, and measuring distance. A foot is equivalent to 12 inches, and feet are often used to express height ordistance in a more manageable form compared to inches.

In contrast, the other options refer to units that are unrelated to length: a milligram measures mass, a liter measures volume, and a teaspoon is used for measuring small volumes, particularly in cooking. Therefore, 'ft' specifically aligns with the definition of feet as a unit of length, making it the correct choice.