Final answer:
The proper term for a group of swallows is a 'flock', which is indicative of their collective behavior. This is in line with how various animal groups are referred to by distinct terms such as 'school' for fish and 'herd' for cattle.
Step-by-step explanation:
When referring to a group of grey swallows that takes off in the distance, the correct term from the given options to describe this collective behavior of birds is a 'flock'. Other groups of different animals have specific terms that are used to describe their collective behavior; for instance, a group of fish is called a 'school', and they are known for swimming in coordinated patterns. Similarly, cattle traveling together are referred to as a 'herd', as seen when they stampede together in response to external stimuli.