Answer:
a. immigration
The thirteen colonies were founded by Immigrants who wanted a better opportunity in their life. They came from all across the world with the hope that they can acquire land with cheap price and struck their rich.
b. epidemic
Many of the immigrants came from European countries during the first wave of the immigrants. A lot of them were carriers of disease such as measles and small pox, from which the native Americans did not have a resistance, So, this caused an epidemic that killed large number of native Americans.
c. apprentice
A lot of the people came into the colonies without any particular skills. So, many craftman often opened up apprenticeship. In this program, the craftmans will teach various knowledge to the non-skilled immigrants. In return, those immigrants will work for the craftmans for a specific period of time.
d. civic virtue
Civic virtue refers to a standards of behaviors that's generally considered as righteous within the society. During early settlement, the colonies did not possess a government that impose a strict implementation of laws. Si, they relied on civic virtue to maintain the order in their society.