Which of the following dimensions qualifies a parcel as irregular?

A parcel is typically considered irregular when it does not meet standard size and weight criteria set by postal services. In this context, a length of less than 6 inches can indicate that the item does not conform to the usual dimensions for standard parcels, which may affect how it is processed and shipped.

An irregular parcel often refers to items that are either too small, too large, or shaped in a way that doesn't fit within the established guidelines for regular mail. When the length is below a specific threshold, such as 6 inches, it signifies that the item may be too small to qualify for regular rates, making it irregular.

In contrast, the other options focus on weight, height, or specific lengths that do not accurately align with common criteria for defining irregular parcels. For example, a weight of less than 8 ounces may still fall within the realm of regular shipping options, as many postal services have weight classes that accommodate lightweight items. Similarly, a height greater than 3 inches or a length of more than 12 inches might also qualify as standard dimensions, depending on the other measurements involved. Therefore, the defining characteristic here is the length being below the recognized minimum for regular parcels, which makes it irregular.