With iron tools. farmers were able to clear land more efficentaly
Atlantic ocean i live here i would know :p
Answer:
omg the question is really really long sry but don't know
Earth is a round planet made up of layers. The inner core, an outer core, the lower mantle, the upper mantle, and the outer solid crust. The earth is 61 degrees F (16 C). The earth is made up of iron and nickel. In fact, the earth is made up of oxygen (46%), silicon (27.7%), aluminum (8.1%), iron (5%), and calcium (3.6%). Composition of the Earth.
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The threat to validity that is likely to occur in the scenario above is Selection Bias.
<h3>What is Selection Bias?</h3>
This occurs when a researcher has control and intentionally chooses those who are going to be researched, observed, or studied. To eliminate this bias, the scientist must ensure that the sample population is selected very randomly.
Other threats to validity are:
- History
- Maturation
- Attrition
- Social Interaction
- Instrumentation
- Testing
- Regression to the mean, etc.
Please see the link below for more about Threat to Validity:
brainly.com/question/4168290
