A soft ferromagnetic material is placed in an external magnetic field. The magnetic domains:

In a ferromagnetic material, the atomic magnetic dipoles are grouped into regions called magnetic domains. Within each domain, the dipoles are aligned in the same direction, but different domains may point in different directions.

When a soft ferromagnetic material is placed in an external magnetic field, the domains respond in two ways. First, the domains whose magnetic moments are aligned (or nearly aligned) with the external field tend to grow in size at the expense of neighbouring domains that are less favourably oriented. This is called domain wall motion. Second, the magnetic moments of individual domains may rotate to align more closely with the applied field direction. This is called domain rotation.

Depending on the strength and direction of the external field relative to each domain's initial orientation, some domains increase in size while others decrease. Additionally, the orientation of domains changes to align with the field. In a soft ferromagnetic material, both these processes occur readily because the domain walls move easily.

Therefore, the magnetic domains may increase or decrease in size and change their orientation.

The correct answer is that domains may increase or decrease in size and change its orientation.