The experimental results could be made more valid 1) increasing the number of students. 2) using a plastic clothespin. 3) using safety precautions. 4) making a bar graph of the data.

Countries trade with each other when, on their own, they do not have the resources, or capacity to satisfy their own needs and wants. By developing and exploiting their domestic scarce resources, countries can produce a surplus, and trade this for the resources they need. You can integrate all of this into your question. Hope this helped.