Mountains because when two tectonic plates interact they create mountains
1. A- the economy faced serious challenges
2. B- Modernized
I would say D the Billingsella Corrugata, it IS in the oldest recorded time line, so by theory, it's the oldest (Don't quote me on that, I'm not %100)
<span>The major river of Venezuela's iron-rich eastern region is the Orinoco, meaning the answer is D. Orinoco.</span>