Answer:
The correct answer is d. Some groups are just people assembled together in the same physical area.
Explanation:
There may be times when there is a very large group of people who concentrate because they coincide in a place and time, which does not mean that they necessarily share the same ideals. It is enough with a confirmation question to realize what it is that they are gathered.
In the workplace, people may be concentrated because they need to hear a message transmitted by an organization official, who may or may not be their immediate boss.
