I think the awnser to your question is C
I THINK it's <span>1,1-Difluorononane, or </span>

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D. Model number 2
Hope this helps!! (:
Can you reword it im confused
When two air masses meet together, the boundary between the two is called a weather front. At a front, the two air masses have different densities, based on temperature, and do not easily mix. One air mass is lifted above the other, creating a low pressure zone.