German cockroaches must be __________ to enter a building.

German cockroaches are typically not indigenous to indoor environments; rather, they usually enter buildings through transportation from outdoors. This means they often hitch a ride on items or luggage brought into the building, or they may come through cracks and crevices from adjacent structures. Their survival in homes is largely due to human activity, which provides food, water, and shelter.

The concept that they must be "transported from outdoors" captures the primary way these pests infiltrate residences and commercial buildings. Unlike some other species of cockroaches that might originate from indoors, German cockroaches are not born and raised in exterior environments—they rely on being moved inside by humans or through infested items.

Other options do not accurately represent the common behavior of German cockroaches. For instance, although they can be attracted by smells, this is not a necessary condition for their entry; they can enter regardless of odor if they are transported. Saying they must be left open to enter also implies a passive process not characteristic of cockroach behavior, which is more opportunistic and active. Thus, it is essential to understand their reliance on transportation for their entry into buildings, as it highlights both how infestations begin and how they can be mitigated by preventing the movement of