Answer: Public Good
Explanation:
In medieval Europe an important technological advance was the use of the padded horse collar for plowing.
Once this idea was thought of, other people used it. This illustrates that knowledge is generally a public good.
Answer:2. Snowball sampling
Explanation: Snowball sampling refers to a research in which once participants behave been recruited for a study they can also recruit other participants that they know. This is useful when it is hard for a researcher to find potential participants. The name of this research comes from the fact that when you roll down the ball made from snow it will pick up some other particles along the way and it will keep getting bigger and bigger.
I believe this one is "true"