Akey characteristic of a civilization is the specialization of labor. what does this mean?
people are self-sufficient economically.
all people depend on the work of others.
everyone gets to decide what type of work they'd like to do.
every family is in charge of a certain trade.

Option 2: All people depend on the work of others.

Within the formation of larger and more complex societies, people found useful the specialization of labor to enhance productivity, efficiency and quality of the good or service given. With such specialization, a person didn't have to learn how to do every kind of work, and at the same time, it made every individual rely on the work of others so he/she could get what they needed.

For example, in a civilization, the person whose skill consists of merely making shoes, makes her own shoes, however, he/she still needs clothes, and inevitably depends on the work of clothing makers. And the clothing makers need the shoemakers, and so on and so for.

pls be more elaborate

the answer for 3 is b and the answer for 4 is d